Showing papers in "Biometals in 1998"
TL;DR: An evaluative model is presented as a reference for the quantitative analysis of the susceptibility of bacteria to silver ions and one log-unit of viable bacterial population size was lost every 30 min at the minimum bactericidal concentration of the silver ion.
Abstract: The susceptibility of Escherichia coli B to the antibacterial activity of silver ions was measured in terms of the initial inhibitory concentration, complete inhibitory concentration, postagent effect for bacteriostatic susceptibility, minimum bactericidal concentration, maximum tolerant concentration, and log killing time for bactericidal activity. At a concentration of 9.45 μM and an inoculum size of 10 CFU ml, silver caused growth delay of E. coli; at a concentration of 18.90 μM, silver completely inhibited bacterial growth. Prolonged postagent effects ranged between 1.5 and 12 h at 0.75 x the initial inhibitory concentration, 1.0 x the initial inhibitory concentration, and 1.5 x the initial inhibitory concentration of the silver ion. One log-unit of viable bacterial population size was lost every 30 min at the minimum bactericidal concentration of the silver ion. Silver tolerance was determined as 20 times the initial inhibitory concentration with 48 h of exposure. This study presents an evaluative model as a reference for the quantitative analysis of the susceptibility of bacteria to silver ions. © Rapid Science 1998.
543 citations
TL;DR: Forty-five distinct subfamilies of EF-hand proteins have been identified; many sequence and chem-ical characteristics do not show systemic trends by subfamily or species of host organisms; such homoplasy is widespread.
Abstract: Forty-five distinct subfamilies of EF-hand proteins have been identified. They contain from two to eight EF-hands that are recognizable by amino acid sequence as being statistically similar to other EF-hand domains. All proteins within one subfamily are congruent to one another, i.e. the dendrogram computed from one of the EF-hand domains is similar, within statistical error, to the dendrogram computed from another(s) domain. Thirteen subfamilies--including Calmodulin, Troponin C, Essential light chain, Regulatory light chain--referred to collectively as CTER, are congruent with one another. They appear to have evolved from a single ur-domain by two cycles of gene duplication and fusion. The subfamilies of CTER subsequently evolved by gene duplications and speciations. The remaining 32 subfamilies do not show such general patterns of congruence; however, some--such as S100, intestinal calcium binding protein (calbindin 9 kd), and trichohylin--do not form congruent clusters of subfamilies. Nearly all of the domains 1, 3, 5, and 7 are most similar to other ODD domains. Correspondingly the EVEN numbered domains of all 45 subfamilies most closely resemble EVEN domains of other subfamilies. Many sequence and chemical characteristics do not show systemic trends by subfamily or species of host organisms; such homoplasy is widespread. Eighteen of the subfamilies are heterochimeric; in addition to multiple EF-hands they contain domains of other evolutionary origins.
361 citations
TL;DR: It appears that the S100-binding domain in some target proteins contains a basic amphiphilic a-helix and that the mode of interaction and activation bears structural similarity to that of calmodulin.
Abstract: S100 proteins (16 members) show a very divergent pattern of cell- and tissue-specific expression, of subcel-lular localizations and relocations, of post-translational modifications, and of affinities for Ca 2+ , Zn 2+ , and Cu 2+ , consistent with their pleiotropic intra- and extracellular functions. Up to 40 target proteins are reported to interact with S100 proteins and for S100A1 alone 15 target proteins are presently known. Therefore it is not surprising that many functional roles have been proposed and that several human disorders such as cancer, neurodegenerative diseases, cardiomyopathies, inflammations, diabetes, and allergies are associated with an altered expression of S100 proteins. It is not unlikely that their biological activity in some cases is regulated by Zn 2+ and Cu 2+ , rather than by Ca 2+ Despite the numerous putative functions of S100 proteins, their three-dimensional structures of, e.g., S100B, S100A6, and S100A7 are surprisingly similar. They contain a compact dimerization domain whose conformation is rather insensitive to Ca 2+ binding and two lateral a-helices III and III, which project outward of each subunit when Ca 2+ is bound. Target docking depends on the two hydrophobic patches in front of the paired EF-hand generated by the binding of Ca 2+. The selec-tivity in target binding is assured by the central linker between the two EF-hands and the C-terminal tail. It appears that the S100-binding domain in some target proteins contains a basic amphiphilic a-helix and that the mode of interaction and activation bears structural similarity to that of calmodulin.© Kluwer Academic Publishers
297 citations
TL;DR: The classical picture of calcium sensors and calcium signal modulators is presented, along with variants on the basic theme and new structural paradigms.
Abstract: The growing database of three-dimensional structures of EF-hand calcium-binding proteins is revealing a previously unrecognized variability in the coformations and organizations of EF-hand binding motifs. The structures of twelve different EF-hand proteins for which coordinates are publicly available are discussed and related to their respective biological and biophysical properties. The classical picture of calcium sensors and calcium signal modulators is presented, along with variants on the basic theme and new structural paradigms.© Kluwer Academic Publishers
213 citations
TL;DR: In this chapter various aspects of apoptosis or programmed cell death influenced by calcium as a mediator of signal transduction have been reviewed and Calcineurin, which normally is involved in the regulation of T-cell proliferation, is reported to interact with the apoptosis protec-tion protein bcl-2.
Abstract: In this chapter various aspects of apoptosis or programmed cell death (PCD) influenced by calcium as a mediator of signal transduction have been reviewed. Attention has been focused on recently described calcium-binding proteins such as ALG-2 or on a new calcium/calmodulin-dependent kinase, the death associated protein kinase or DAP-kinase. Both play a central role in apoptotic processes. Calcineurin, which normally is involved in the regulation of T-cell proliferation, is reported to interact with the apoptosis protection protein bcl-2. Its possible involvement in the decision process whether T-cell activation leads to proliferation or apoptosis is discussed.
199 citations
TL;DR: Identification of intermediates and potential processes from uptake of the toxic oxyanions through to their detoxification will assist in understanding the complexities of metalloid oxyanion metabolism in these bacteria.
Abstract: Escherichia coli will reduce selenite (SeO3(2-)) and selenate (SeO4(2-)) to elemental selenium Se0. Selenium will also become incorporated into proteins as part of the amino acids selenocysteine or selenomethionine. The reaction of selenite with glutathione produces selenodiglutathione (GS-Se-GS). Selenodiglutathione and its subsequent reduction to glutathioselenol (GS-SeH) are likely the key intermediates in the possible metabolic fates of selenium. This review presents the possible pathways involving selenium in E. coli. Identification of intermediates and potential processes from uptake of the toxic oxyanions through to their detoxification will assist us in understanding the complexities of metalloid oxyanion metabolism in these bacteria.
198 citations
TL;DR: The results suggest that Cd intoxication induces oxidativestress and alters the antioxidant system, resulting in oxidative damage torat erythrocytes, probably in an attempt to reduce Cd toxicity.
Abstract: Cadmium induced lipid peroxidation (LPO) and the activity of antioxidantenzymes after the administration of a single dose of CdCl 2 (0.4 mg kg body wt, ip) was studied in rat erythrocytes.Cd intoxication increased erythrocyte LPO along with a decrease insuperoxide dismutase (SOD) up to three days of Cd treatment. Thedecrease in erythrocyte catalase (CAT) activity was marked within9 h of Cd intoxication. After three days of Cd treatment, LPOdecreased towards normal, along with an increase in erythrocyteSOC and CAT activity. Blood glutathione (GSH) decreased significantlywithin 24 h of Cd treatment, followed by an increase towards normal.Erythrocyte glutathione S-transferase (GST) activity increased up to10 days of Cd intoxication, probably in an attempt to reduce Cd toxicity.Serum glutamate pyruvate transaminase (SGPT), serum alkaline phosphatase(SALP) and serum bilirubin increased up to 10 days of Cd intoxication.Blood urea increased significantly up to three days, followed by a decreasetowards normal. The results show that Cd induced LPO was associated with adecrease in antioxidant enzymes and GSH in erythrocytes; as these antioxidantsincrease in erythrocytes with recovery from Cd intoxication, the Cd inducedLPO reversed towards normal. The increase in the SGPT, SALP and serum bilirubincorrelated with LPO. The results suggest that Cd intoxication induces oxidativestress and alters the antioxidant system, resulting in oxidative damage torat erythrocytes. © Rapid Science 1998
136 citations
TL;DR: The slight viral inhibition shown by the citrate complexes of the different metals could indicate that the antiviral effect was not significantly influenced by Fe, Mn or Zn ions delivered by BLf into the cells.
Abstract: The inhibitory effect of bovine lactoferrin (BLf) saturated with ferric, manganese or zinc ions, on the infection of Vero cells by human herpes simplex virus type 1 (HSV1) and 2 (HSV2) was investigated. Viral infectivity determined by intracellular antigen synthesis and plaque formation was efficiently inhibited by metal saturated lactoferrins in a dose-dependent manner. Effective BLf concentrations which reduced the infection by 50% ranged from 5.2 to 31 mug ml and were far below the cytotoxicity threshold. Fe BLf and Mn BLf exhibited selectivity indexes higher than Zn BLf and apoBLf for both viruses and the effect was mainly directed towards the early steps of infection. The slight viral inhibition shown by the citrate complexes of the different metals could indicate that the antiviral effect was not significantly influenced by Fe , Mn or Zn ions delivered by BLf into the cells. © Rapid Science 1998
94 citations
TL;DR: The results indicate that accumulation of both tellurium and chromium occurred mainly in the cytosolic compartment of the cell, with detoxification influenced by the presence of a functionally-active vacuole which may play a role in compartmentation as well as regulation of the cytostolic compartment for optimal expression of a detoxification mechanism, e.g. reduction.
Abstract: The responses of Saccharomyces cerevisiae towards the oxyanions tellurite, selenite and chromate were investigated in order to establish the involvement of the yeast vacuole in their detoxification. Three mutants of S. cerevisiae with defective vacuolar morphology and function were used; mutant JSR180D1 is devoid of any vacuolar-like structure while ScVatB and ScVatC are deficient in specific protein subunits of the vacuolar (V)-H -ATPase. All the mutant strains showed increased sensitivity to tellurite and chromate compared to their parental strains. Such sensitivity of the mutants was associated with increased accumu-lation of tellurium and chromium. These results indicate that accumulation of both tellurium and chromium occurred mainly in the cytosolic compartment of the cell, with detoxification influenced by the presence of a functionally-active vacuole which may play a role in compartmentation as well as regulation of the cytostolic compartment for optimal expression of a detoxification mechanism, e.g. reduction. In contrast, the vacuolar-lacking mutant, JSR180D1, and the defective V-H ATPase mutant ScVatB displayed lower selenium accu-mulation than their parental strains. Additionally, the mutant strain ScVatB displayed a higher tolerance to selenite than the parental strain. This result suggests that accumulation of selenium occurs mainly in the vacuolar compartment of the cell with tolerance depending on the ability of the cytosolic component to reduce selenite to elemental selenium, which might, in turn, be related to activity of the V-H -ATPase. These results are discussed in relation to vacuolar compartmentation and the significance of the vacuolar H -ATPase in cytosolic homeostasis of H both of which may affect the accumulation, reduction, and toler-ance to the tested metal(loids). © Rapid Science 1998
85 citations
TL;DR: The features of CREB activation by calcium signals in mammalian cells are reviewed and its regulation is dependent on an elevation of nuclear calcium concentration, potentially placing this spatially distinct pool of calcium as an important mediator of information storage.
Abstract: Through the evolution of multicellular organisms, calcium has emerged as the preferred ion for intracel-lular signalling. It now occupies a pivotal role in many cell types and nowhere is it more important than in neurons, where it mediates both the relaying and long-term storage of information. The latter is a process that enables learning and memory to be formed and requires the activation of gene expression by calcium signals. Evidence from a number of diverse organisms shows that transcription mediated by the transcrip-tion factor CREB is critical for learning and memory. Here we review the features of CREB activation by calcium signals in mammalian cells. In contrast to other transcription factors, its regulation is dependent on an elevation of nuclear calcium concentration, potentially placing this spatially distinct pool of calcium as an important mediator of information storage.© Kluwer Academic Publishers
70 citations
TL;DR: The data suggest that the toxicity of Pb-which, like Sr, binds with an equal and high affinity to all four sites-may be related to its capacity to tightly bind and improperly activate calmodulin.
Abstract: Calmodulin is an important second messenger protein which is involved in a large variety of cellular path-waysCalmodulin is sensitive to fluctuations in the intracellular Ca levels and is activated by the bindingof four Ca ions In spite of the important role it plays in signal transduction pathways, it shows a surpris-inglybroad specificity for binding metal ions Using 15N-Gly biosynthetically-labelled calmodulin, we havestudied the binding of different metal ions to calmodulin, including K+, Na+, Ca, Mg, Zn, Cd, Pb, Hg, Sr, La and Lu, by 1H, 15N HMQC NMR experiments The effects of these ions on the substrate-bindingability of calmodulin have also been studied by fluorescence spectroscopy of the single tryptophan residue in a 22-residue synthetic peptide encompassing the skeletal muscle myosin light chain kinase calmod-ulin-binding domain Most of these metal ions can activate a calmodulin target enzyme to some extent,though they bind to calmodulin in a different manner Mg, which is of direct physiological interest, has adistinct site-preference for calmodulin, as it shows the highest affinity for site I in the N-terminal domain,while the C-terminal sites III and IV are the high affinity binding sites for Ca (as well as for Cd ) At ahigh concentration of Mg and a low concentration of Ca, calmodulin can bind Mg in its N-terminallobe while the C-terminal domain is occupied by Ca; this species could exist in resting cells in which the Mg level significantly exceeds that of Ca Moreover, our data suggest that the toxicity of Pb-which,like Sr, binds with an equal and high affinity to all four sites-may be related to its capacity to tightlybind and improperly activate calmodulin
TL;DR: The focus of this review is to describe the biochemical regulation of CaMK IV and examine how CaMKIV activates tran-scription in response to calcium in both cell and animal models.
Abstract: Ca2+/calmodulin dependent protein kinase IV (CaMKIV) is a multifunctional, serine-threonine protein kinase that is activated in the presence of increased intracellular calcium (Ca2+). CaMKIV is a potent mediator of Ca2+ induced gene expression, primarily through its ability to phosphorylate and activate transcription factors such as CREB. CaMKIV-dependent activation of CREB is a key event in the expression of genes involved in the processes of T-cell activation and neuronal long term potentiation. The focus of this review is to describe the biochemical regulation of CaMKIV and examine how CaMKIV activates transcription in response to calcium in both cell and animal models.
TL;DR: The present study demonstrates that the alteration of cytochrome c oxidase activity observed in copper deficiency is due to a diminished content of assembled protein and that shortness of copper impairs heme insertion into cy tochrome c oxidation.
Abstract: Copper deficiency has been reported to be associated withdecreased cytochrome c oxidase activity, whichin turn may be responsible for theobserved mitochondrial impairment and cardiac failure We isolatedmito-chondriafrom hearts of copper-deficient rats: cytochrome c oxidase activity was found to be lowerthan incopper-adequate mitochondria The residual activity paralleled coppercontent of mitochondria and also corresponded with the heme amount associated with cytochromeaa3 In fact, lower absorption in thea-band region of cytochrome aa3 was foundfor copper-deficient rat heart mitochondria Gel electrophoresisof protein extractedfrom mitochondrial membranes allowed measurements of protein content of thecomplexes ofoxidative phosphorylation, revealing a lower content of complex IV protein incopper-deficientrat heart mitochondria The alterations caused by copper deficiency appear to bespecific forcytochrome c oxidase Changes were not observed for F 0 F 1 ATP synthase activity,for heme contents ofcytochrome c and b, and for protein contents of complexes I, III and VThe present study demonstrates that the alteration of cytochrome c oxidase activityobserved in copper deficiency is due to a diminishedcontent of assembled protein and that shortnessof copper impairs heme insertion into cytochrome c oxidase
TL;DR: This study has been to analyse solved X-ray structures for inter-actions common in both the manganese and iron forms and those that are specific to each, which may indi-cate reasons for the metal ion specificity.
Abstract: There are two types of homologous enzymes catalysing the dismutation of the superoxide radical--Cu-Zn superoxide dismutases, and manganese or iron superoxide dismutases. In the latter two forms there is a high percentage of identity in the primary structures, and the tertiary structures are very similar particularly in the areas of the active site and in the residues responsible for the formation of the dimer. The quaternary structure of the dimer is also highly conserved. However, it has been found that despite this conservation there is strong metal ion specificity and many enzymes in the family will only be active if the correct metal ion is present. The purpose of this study has been to analyse solved X-ray structures for interactions common in both the manganese and iron forms and those that are specific to each, which may indicate reasons for the metal ion specificity. Initial analysis points to the probability that it is a combination of a number of residues, and not necessarily the same ones in every instance, which confer the specificity. In addition we have identified some anomalies in the currently available Fe/MnSOD structures which may require further remodelling and refinement.
TL;DR: A number of the possible isoforms for both types of proteins has been detected and these transporters control the Ca 2+ concentration in the cytosol and are vital to prevent Ca 2- overload of the cells.
Abstract: The Ca2+ ATPases or Ca2+ pumps transport Ca2+ ions out of the cytosol, by using the energy stored in ATP. The Na+/Ca2+ exchanger uses the chemical energy of the Na+ gradient (the Na+ concentration is much higher outside than inside the cell) to remove Ca2+ from the cytosol, Ca2+ pumps are found in the plasma membrane and in the endoplasmic reticulum of the cells. The pumps are probably present in the membrane of other organelles, but little experimental information is available on this matter. The Na+/Ca2+ exchangers are located on the plasma membrane. A Na+/Ca2+ exchanger was found in the mitochondria, but very little is known on its structure and sequence. These transporters control the Ca2+ concentration in the cytosol and are vital to prevent Ca2+ overload of the cells. Their activity is controlled by different mechanisms, that are still under investigation. A number of the possible isoforms for both types of proteins has been detected.
TL;DR: Measurements of cell cycle indicated that the metal ions arrested the transitions from G /G to S state, and growth rates of melanoma cells in the presence of 1 mM of metal ions were significantly lower than that of control cells.
Abstract: The effects of trivalent metal ions such as lanthanoid (La , Ce, Nd , Sm , Gd , Er , Yb , Lu ) and Al ions on the morphological change and proliferation of B16 melanoma cells in culture are discussed. These metal ions induced morphological transformations and decreased growth rates at doses of 1 mM. B16 melanoma cells treated with La , Ce , Nd , Sm , and Gd showed polyhedrical spreading. Elongation of axones was dependent on the metal ions. B16 melanoma cells treated with Er , Yb , Lu , and Al showed a long slender shape. Growth rates of melanoma cells in the presence of 1 mM of metal ions (La , Ce , Nd , Sm , Gd , Yb , Al ) were significantly lower than that of control cells. Measurements of cell cycle indicated that the metal ions arrested the transitions from G /G to S state. © Rapid Science 1998
TL;DR: All three microorganisms tested for their ability to recover gold from gold–thiourea solutions can therefore be used in biotechnological applications, especially Spirulina platensis which has the highest binding capacity for gold at low pH values.
Abstract: The recovery of gold from gold-thiourea solutions using various types of waste biomass was investigated. All organisms tested, namely, Saccharomyces cerevisiae, Spirulina platensis and Streptomyces erythraeus removed gold rapidly from gold–thiourea solutions. The process of gold accumulation was pH-dependent for Saccharomyces ceresvisiae and Streptomyces erythraeus and independent of pH in the case of Spirulina platensis. Of all strains of microorganisms examined, Spirulina platensis had the highest affinity and capacity for gold even at low pH values. Thus, all three microorganisms tested for their ability to recover gold from gold–thiourea solutions can therefore be used in biotechnological applications, especially Spirulina platensis which has the highest binding capacity for gold at low pH values. © Rapid Science 1998
TL;DR: Conjugates of a carbacephalosporin with hydroxamate, spermexatol, N,N-bis(2,3-dihydroxybenzoyl)-L-lysine, mixed catecholate/hydroxamate and cyanuric acid-based siderophores were investigated for their potential to promote growth and antibacterial activity, and for their ability to use iron transport path-ways to penetrate the Gram-negative bacterial outer membrane.
Abstract: Conjugates of a carbacephalosporin with hydroxamate, spermexatol, N alpha,N epsilon-bis(2,3-dihydroxybenzoyl)-L-lysine, mixed catecholate/hydroxamate and cyanuric acid-based siderophores were investigated for their potential to promote growth of siderophore indicator strains of Gram-negative and Gram-positive bacteria under iron depleted conditions, for their antibacterial activity and for their ability to use iron transport pathways to penetrate the Gram-negative bacterial outer membrane. The selective growth promotion of enterobacterial and pseudomonas strains by hydroxamate, spermexatol and mixed catecholate-hydroxamate siderophore-based conjugates bearing a L- or D-amino acid spacer was correlated with TonB dependent uptake routes. The preferred outer membrane siderophore receptor used in Escherichia coli was found to be Fiu, followed by Cir. Antagonistic effects of siderophores administered with the conjugates to determine antibacterial activity confirmed the active transport of conjugates via siderophore receptors. All of the conjugates were still able to diffuse through the porin proteins OmpC and OmpF. Nevertheless, strong inhibition of E. coli and Pseudomones aeruginosa outer membrane mutants DC2 and K799/61 compared to the parent strains indicated inefficient penetrability of all types of conjugates tested. Mycobacterium smegmatis SG 987 was able to use all of the siderophore-cephalosporin conjugates as growth promotors. Consequently there was no growth inhibition of this strain.
TL;DR: A transient rise in BP was observed following Gd-HP-DO3A, another macrocyclic chelate, associated with a concomitant increase in stroke volume, and this effect was antagonized neither by phentolamine nor by diltiazem.
Abstract: Several studies were undertaken to compare four magnetic resonance imaging (MRI) contrast media (CM) as regards acute haemodynamic effects in rats and to investigate the mechanisms involved. (1) Normotensive rats received a rapid bolus intravenous injection of 0.5 mmol kg of each CM. The effects of Gd-DOTA, Gd-HP-DO3A, Gd-DTPA and Gd-DTPA-BMA on blood pressure (BP) were compared. (2) The haemo-dynamic effects of Gd-DTPA (0.5 mmol kg ) were compared to those of isovolumic and isoosmolar Zn-DTPA and glucose solutions. (3) The haemodynamic profiles of Gd-DTPA and Gd-DTPA-BMA were recorded with and without addition of ionized calcium. (4) The mechanism of Gd-HP-DO3A-induced tran-sient rise in BP was investigated by evaluating the effects of phentolamine or diltiazem pretreatment. For (1) the greatest drop in BP occurred following Gd-DTPA (a linear chelate) injection (–18 ± 2% vs base-line, P < 0.01). Gd-DTPA-BMA, another lineate chelate, also induced a slight but significant reduction in BP (–8 ± 2% at 45 s, P < 0.05). Gd-DOTA, a macrocyclic CM, had virtually no haemodynamic effects. For (2) the Gd-DTPA-induced drop in BP was greater than that of the osmolality-matched glucose control and lower than that of osmolality-matched Zn-DTPA. For (3) a transmetallation phenomenon versus free ionized calcium is possible in the case of both linear CM (Gd-DTPA and Gd-DTPA-BMA) since Ca significantly reduced the CM-induced decrease in BP. For (4) a transient rise in BP was observed following Gd-HP-DO3A, another macrocyclic chelate, associated with a concomitant increase in stroke volume. This effect was antagonized neither by phentolamine nor by diltiazem. The decrease in BP following injection of Gd-DTPA or Gd-DTPA-BMA may not only be osmolality-related since (a) Gd-DOTA solution, whose osmo-lality is greater than that of Gd-DTPA-BMA, had a lesser effect, and (b) this hypotensive effect was corrected by addition of ionized calcium. The transient Gd-HP-DO3A-induced rise in BP is probably the consequence of a positive inotropic effect. © Rapid Science 1998
TL;DR: The results imply that either there is a selected targeting of iron to the brain by plasma Tf or there is an alternative irondelivery system tothe brain, and that there are non-Tf dependent mecha-nisms for Mntransport.
Abstract: Hypotransferrinemia is a genetic defect in mice resulting < 1% of normal plasma transferrin (Tf) concentrations; heterozygotes for this mutation (+/hpx) have low circulating Tf concentrations. These mice provide a unique opportunity to examine the developmental pattern and response of Tf to iron-deficient diets, and furthermore, to address the controversial role of Tf in Mn transport. Twenty-three weanling +/hpx mice and forty-five wild-type BALB/cJ mice were either killed at weaning or fed diets containing either 13 or 72 mg kg-1 Fe, and killed after four or eight weeks. Plasma Tf concentrations were lower in +/hpx mice, plasma Tf nearly doubled and liver Tf was only 50% of normal in response to iron deficiency. Brain iron concentration did not correlate significantly with either plasma Tf or TIBC. However, iron accumulation into brain continued with iron deficiency whereas most other organs had less iron. These results imply that either there is a selected targeting of iron to the brain by plasma Tf or there is an alternative iron delivery system to the brain. Furthermore, we observed no differences in tissue distribution of 54Mn despite the differences in circulating Tf concentrations and body iron stores; this suggests that there are non-Tf dependent mechanisms for Mn transport.
TL;DR: The structure of a chloroform-extractable siderophore from the supernatant of a nonpathogenic mycobacteria, Mycobacterium smegmatis, has been determined and the name 'carboxymycobactin' is proposed to distinguish it from mycOBactin itself as well as from the major siderophile that is produced - exochelin MS.
Abstract: The structure of a chloroform-extractable siderophore from the supernatant of a nonpathogenic mycobacteria, Mycobacterium smegmatis, has been determined and it closely resembles the structure of mycobactin, the intracellular siderophore found in all mycobacteria. The difference in structures is that the extracellular siderophore has a family of short carboxylic chains attached to the mycobactin nucleus instead of a long alkyl chain and hence the name 'carboxymycobactin' is proposed to distinguish it from mycobactin itself as well as from the major siderophore that is produced - exochelin MS. © Rapid Science 1998.
TL;DR: There were no apparent trends for the levels of any metals versus age nor were there any differences in average hepatic metal concentrations for males and females.
Abstract: Autopsied liver tissue samples collected from 42 males and 31 females were analyzed for copper, manganese and zinc using atomic absorption spectrometry (AAS). With the exception of two liver samples for which the copper levels were determined to be 74.8 and 104.0 μg/g (dry weight), hepatic copper concentrations were found to range from 1.7 to 32.4 μg/g with a mean concentration of 14.2 μg/g and standard deviation of 7.0 μg/g. Manganese concentrations (with the exception of one sample having 12.9 μg/g) ranged from 0.22 to 4.6 μg/g with a mean of 2.26 ± 1.00 μg/g. Hepatic zinc levels averaged 118.3 ± 44.4 μg/g and ranged from 38.5 to 231.3 μg/g. There were no apparent trends for the levels of any metals versus age nor were there any differences in average hepatic metal concentrations for males and females. © Rapid Science 1998.
TL;DR: ESR spectra indicate that the copper cluster in the membrane fraction is reduced by duroquinol and oxidized by dioxygen, suggesting that the Copper cluster is contained in the active site of pMMO.
Abstract: The particulate methane monooxygenase (pMMO) from Methylosinus trichosporium OB3b was partially purified and characterized by measuring the effects of reducing agents and additives, and the stability of pMMO was studied. Duroquinol was a suitable reducing agent, and pMMO was stabilized by bovine serum albumin (BSA). Among the additives, the copper (II) ion stimulated pMMO at low concentration and inhibited at high concentration. The optimum conditions for pMMO activity were as follows: 45 degrees C, pH 6.5 and 55 mM 3-morpholinopropanesulfonic acid (MOPS) buffer, and the rate of propene epoxide formation was 13.6 nmol min-1 mg-1 protein. ESR spectra indicate that the copper cluster in the membrane fraction is reduced by duroquinol and oxidized by dioxygen. The result suggests that the copper cluster is contained in the active site of pMMO.
TL;DR: A functional analysis of FoxA and FoxA receptors cloned into a Fhu-negative background revealed that ferrioxamines are recognized at very low concentrations (< 10 pmoles) in growth promotion bioassays, andCoprogen was also recognized to a certain extent, whereas ferrichromes were completely excluded from the FoxA receptor, confirming that coprogens share some structural similarities with the ferRIoxamines.
Abstract: The outer membrane receptor for ferrioxamines (FoxA Erw ) of Erwinia herbicola (Pantoea agglomerans) was cloned from a cosmid gene bank and partially sequenced. A comparison of the partial amino acid sequence of FoxA with the amino acid sequence of FoxA Yer from Yersinia enterocolitica revealed a high sequence homology. A functional analysis of FoxA and FoxA receptors cloned into a Fhu-negative background (HK97) revealed that ferrioxamines are recognized at very low concentrations (< 10 pmoles) in growth promotion bioassays. A collection of ferrioxamine derivatives containing varying chain lengths and ether bridges within the molecule was also accepted. However, the three ether containing ferrioxamine (Et ) behaved differently in the two FoxA receptors. Coprogen was also recognized to a certain extent, whereas ferrichromes were completely excluded from the FoxA receptors, confirming that coprogens share some structural similarities with the ferrioxamines. FoxA mutants (FM13) of Erwinia herbicola obtained by ferrimycin selection showed no uptake of Fe-labelled ferrioxamine E and B any more, while the transport of coprogen and ferrichrome was unaffected or even slightly increased. © Rapid Science 1998
TL;DR: This study examined bonding interactions between the copper(II) complex and human serum albumin (HSA) to help elucidate the mode of transport of the complex in vivo and concluded that any ternary complexes formed in the presence of HSA are below the spectroscopic detection limits.
Abstract: The copper(II) complex of 3,5-diisopropylsalicylate is a lipophilic water-insoluble binuclear complex, Cu(II) (3,5-DIPS) , that has attracted interest because of a wide range of pharmacological activities. This study was undertaken to examine bonding interactions between the complex and human serum albumin (HSA) to help elucidate the mode of transport of the complex in vivo. Electron paramagnetic resonance, numerical magnetic resonance and UV-visible absorption spectroscopic studies were performed using 200 μM aqueous solutions (pH 7.5) of HSA to which had been added up to three molar equivalents of CuCl , CuSO , or Cu(II) (3,5-DIPS). Both EPR and UV-visible spectra demonstrated the presence of more than one copper bonding site on HSA, and proton NMR spectra showed that the 3,5-DIPS ligand is also bonded to HSA. These results indicate that there is no observable direct coordination of the ligand to copper in the presence of HSA, and that the majority of the copper and 3,5-DIPS bond to HSA at separate sites. Addition of solid Cu(II) (3,5-DIPS) to HSA at pH 7.5 similarly resulted in spectra that suggest that there are no ternary Cu(II)(3,5-DIPS), Cu(II)(3,5-DIPS) , or Cu(II) (3,5-DIPS) complexes formed with HSA. It is concluded that any ternary complexes formed in the presence of HSA are below the spectroscopic detection limits and represent less than 5% of the total copper. © Rapid Science 1998.
TL;DR: Current information on the calcium-binding characteristics of three classes of cell-surface developmental signaling proteins (EGF-domain proteins, cadherins and integrins) is presented together with an overview of the intra-cellular pathways downstream of these surface receptors.
Abstract: The known roles for calcium-binding proteins in developmental signaling pathways are reviewed. Current information on the calcium-binding characteristics of three classes of cell-surface developmental signaling proteins (EGF-domain proteins, cadherins and integrins) is presented together with an overview of the intracellular pathways downstream of these surface receptors. The developmental roles delineated to date for the universal intracellular calcium sensor, calmodulin, and its targets, and for calcium-binding regulators of the cytoskeleton are also reviewed.
TL;DR: The method of calculating log P described in an article in this journal is faulty for compounds such as PIH, SBH and their analogs whichcontain adjacent hydrophilic groups, and giveserroneous log P values of the iron(III) complexes.
Abstract: Pyridoxal isonicotinoyl hydrazone (PIH), salicylaldehydebenzoyl hydrazone (SBH), and their analogschelate iron(III) and show promise asorally effective drugs for treating diseases of iron overload. Theirbiological activity isrelated to their lipophilicity, as measured by their partition coefficients P betweenn-octanoland water. However, the method of calculating log P described in an article in this journal(Edwardet al. 1995; BioMetals, 8, 209-217) is faulty for compounds such as PIH, SBH andtheir analogs whichcontain adjacent hydrophilic groups. Consequently, the calculations reportedin the article, based on erro-neouslog P values of the chelating molecules, giveerroneous log P values of the iron(III) complexes. Thechelators most effective inmobilizing 59 Fe from reticulocytes have log P < 2.8, not log P < 0 and theiron(III)complexes of the most effective chelators have log P < 3.1, not log P < 0.
TL;DR: Concerted actions between iron carrying albumin and copper carrying ceruloplasmin appear responsible for the production of AFR in vitro and in vivo.
Abstract: The mechanism of ascorbate oxidation by metal-binding proteins (ceruloplasmin, albumin and transferrin) was investigated in vitro and in isolated plasma by the measurement of the ascorbyl free radicals (AFR) by electron spin resonance (ESR). In plasma of 13 healthy volunteers, a spontaneous and variable production of AFR was detected, which was increased by a 10(-4) M ascorbate overloading; however, this increase was not correlated to the intensity of the spontaneous AFR signal. The addition of Cu2+ and ceruloplasmin to plasma increased the ESR signal, while the addition of transferrin decreased the signal intensity in a dose-dependent manner. In vitro, we demonstrated that ascorbate was oxidized by human serum albumin and by ceruloplasmin, and that this oxidase-like activity was lost by trypsin or heat treatment of these proteins. These two proteins positively interacted in the oxidation of ascorbate, since addition of crude albumin to a solution of ascorbate and ceruloplasmin increased the intensity of ESR signal in a dose-dependent manner. The treatment of albumin by a metal chelator (DDTC) abolished these positive interactions. The respective roles of copper and iron in ascorbate oxidation were studied and showed a dose-dependent effect of these ions on ascorbate oxidation. The role of iron was confirmed by the inhibiting effect of metal-free transferrin on iron-dependent ascorbate oxidation. Concerted actions between iron carrying albumin and copper carrying ceruloplasmin appear responsible for the production of AFR in vitro and in vivo.
TL;DR: The data suggest that cadmium interferes with the regulatory mechanism of ACTH, and this work was undertaken to analyze the effects of acutecadmium administration on the episodic pattern ofACTH release in adult male rats.
Abstract: The effects of cadmium on adrenocorticotropin hormone(ACTH) secretion are controversial and seem todepend on the dose and duration ofthe exposure to the metal This work was undertaken to analyze theeffects of acutecadmium administration on the episodic pattern of ACTH release in adult male rats Forthispurpose, animals were cannulated 40 h before the experiment to allow a continuousblood withdrawalTwo and a half hours after the administration of a single dose ofcadmium chloride (45 mg kg bodyweight),the episodic pattern of ACTH wasanalyzed during three hours (from 10:30 to 13:30, samples beingcollectedevery seven minutes) in conscious and freely moving adult male rats The mean valuesof ACTH duringthe bleeding period and the absolute pulse amplitude were decreased byacute cadmium chloride adminis-tration(P < 0001, P < 001, respectively) Bycontrast, the frequency of ACTH pulses increased (P < 001)However, no changes inany other parameters of episodic ACTH secretion were observed compared withcontrolanimals These data suggest that cadmium interferes with the regulatorymechanism of ACTH