Showing papers on "Bovine serum albumin published in 1992"
TL;DR: The use of the thiobarbituric acid (TBA) assay for TBARS of lipid oxidation in extracts of plant materials was examined in this article, where a modified procedure was developed using standard curves for both malondialdehyde (MDA) and sucrose.
Abstract: Use of the thiobarbituric acid (TBA) assay for thiobarbituric acid-reactive substances (TBARS) of lipid oxidation in extracts of plant materials was examined. Sucrose, fructose, glucose, lactose, citrus pectin, and bovine serum albumin (BSA) interfered with the TBA assay reaction. To correct for the interference caused by sugars (the major interference), a modified procedure was developed using standard curves for both malondialdehyde (MDA) and sucrose. Molar absorbance (MA) of adducts from TBA-MDA and TBA-sucrose reactions increased when the acidity in the reaction mixture increased and the time of heating and the temperature of heating for the reaction increased
389 citations
TL;DR: Patients with insulin-dependent diabetes mellitus have immunity to cow's-milk albumin, with antibodies to an albumin peptide that are capable of reacting with a beta-cell--specific surface protein, and such antibodies could participate in the development of islet dysfunction.
Abstract: Background Cow's milk has been implicated as a possible trigger of the autoimmune response that destroys pancreatic beta cells in genetically susceptible hosts, thus causing diabetes mellitus. Studies in animals have suggested that bovine serum albumin (BSA) is the milk protein responsible, and an albumin peptide containing 17 amino acids (ABBOS) may be the reactive epitope. Antibodies to this peptide react with p69, a beta-cell surface protein that may represent the target antigen for milk-induced beta-cell--specific immunity. Methods We used immunoassays and Western blot analysis to analyze anti-BSA antibodies in the serum of 142 children with insulin-dependent diabetes mellitus, 79 healthy children, and 300 adult blood donors. Anti-ABBOS antibodies were measured in 44 diabetic patients at the time of diagnosis, three to four months later, and one to two years later. Results All the diabetic patients had elevated serum concentrations of IgG anti-BSA antibodies (but not of antibodies to other milk proteins), the bulk of which were specific for ABBOS: The mean (+/- SE) concentration was 8.5 +/- 0.2 kilofluorescence units (kfU) per microliter, as compared with 1.3 +/- 0.1 kfU per microliter in the healthy children. IgA antibodies were elevated as well, but not IgM antibodies. The antibody concentrations declined after diagnosis, reaching normal levels in most patients within one to two years. The initial decline involved anti-ABBOS--specific antibodies almost exclusively. Much lower serum concentrations of anti-BSA antibodies were found in all 379 control subjects, but only 2.5 percent of them had small amounts of ABBOS-specific IgG. Conclusions Patients with insulin-dependent diabetes mellitus have immunity to cow's-milk albumin, with antibodies to an albumin peptide that are capable of reacting with a beta-cell--specific surface protein. Such antibodies could participate in the development of islet dysfunction.
373 citations
TL;DR: In this article, four proteins, bovine serum albumin (BSA), calcium-containing and calcium-depleted Bovine α-lactalbumin(BαLA( + Ca2+) and BαLA ( − Ca 2+) respectively) and hen's egg lysozyme (LSZ), were adsorbed from an aqueous solution on to finely dispersed particles of silica and hematite.
223 citations
TL;DR: This factor is found in mouse follicular fluid collected 6 h following human chorionic gonadotropin injection to stimulate ovulation, but not in unstimulated mice, supporting the possibility that this molecule or molecules may diffuse into follicular fluids after an ovulatory stimulus to act as structural linkers that ensure normal cumulus expansion, through stabilization of the cumulus extracellular matrix thus supporting the process of ovulation.
210 citations
TL;DR: It is suggested that, given the fortification of foods with iron and EDTA and the use of phenolic substances as 'antioxidant' food additives, the addition of albumin might afford some protection against damage to deoxyribose and DNA mediated by the above reactions.
199 citations
TL;DR: It was concluded from a mechanistical point of view, that pore-diffusion and bioerosion play an important role on the release of peptides and proteins, but are insufficient to describe the sequelae of events when these systems are exposed to an aqueous environment both in vivo and in vitro.
193 citations
TL;DR: The role of the vascular endothelium in the formation of angiotensin-(1-7) is evaluated and the contribution of proteases released into the medium was evaluated by incubation of 125I-angiotsin I with medium previously incubated for 1 hour with endothelial cells.
Abstract: The heptapeptide angiotensin-(1-7) is a circulating biologically active product of the renin-angiotensin system. In this study, we evaluated the role of the vascular endothelium in the formation of angiotensin-(1-7). Metabolism of 125I-angiotensin I was investigated using confluent cultured bovine and human aortic and umbilical vein endothelial cells. The fetal calf serum-supplemented medium was replaced by serum-free medium containing 0.2% bovine serum albumin. One hour later, this medium was replaced by serum-free medium containing 125I-angiotensin I. After incubation of 125I-angiotensin I for various intervals at 37 degrees C, the medium was collected and analyzed for formed products by high-performance liquid chromatography. Products of angiotensin I metabolism were identified by comparison of their retention times with those of radiolabeled standards. The contribution of proteases released into the medium was evaluated by incubation of 125I-angiotensin I with medium previously incubated for 1 hour with endothelial cells. Incubation of 125I-angiotensin I with bovine and human endothelial cells produced a time-dependent generation of 125I-angiotensin-(1-7) greater than 125I-angiotensin II greater than 125I-angiotensin-(1-4). Generation of angiotensin peptides was not due to the presence of proteases in the medium. When human umbilical endothelial cells were incubated in the presence of the angiotensin converting enzyme inhibitor enalaprilat (1 microM), generation of angiotensin II was undetectable. In contrast, angiotensin-(1-7) production increased by an average of 30%.(ABSTRACT TRUNCATED AT 250 WORDS)
159 citations
TL;DR: The results indicate that gp30 and gp18, unlike gp60, are expressed in all tissues tested regardless of the type of endothelia lining the microvasculature and the local mechanism of transendothelial albumin transport; and A-Au and Mal-BSA bound at the endothelial cell surface were degraded, whereas BSA was not.
148 citations
TL;DR: In this article, both native and denatured protein samples were examined by determining fluorescence and specific rotation, and by polyacrylamide gel electrophoresis (PAGE) and differential scanning calorimetry (DSC).
Abstract: Both native and denatured protein samples were examined by determining fluorescence and specific rotation, and by polyacrylamide gel electrophoresis (PAGE) and differential scanning calorimetry (DSC). Denaturation of ovalbumin by pressure was much less than by heat or by the chemical denaturants. Ovalbumin was denatured under high pressure, as confirmed by the decrease in its a-helical content to 72% and DSC endothermic enthalpy to 61%, but it showed no change in the PAGE pattern. With bovine serum albumin decrease in fluorescence was observed after denaturation by chemicals, but it did not change under high pressure.
147 citations
TL;DR: A method for the determination of the (6R)- and (6S)-stereoisomers of leucovorin using electrokinetic chromatography (EKC) in the affinity mode has been developed and represents a new means of obtaining thermodynamic data for substrate binding interactions and for the general study of drug cross-reactions and interactions of drugs with serum and other proteins.
Abstract: A method for the determination of the (6R)- and (6S)-stereoisomers of leucovorin using electrokinetic chromatography (EKC) in the affinity mode has been developed. Bovine serum albumin (BSA) is used as a run buffer additive to incorporate enantiomeric selectivity into the system. Protein-wall interactions are minimized by using a poly(ethylene glycol) (PEG) coated capillary. Chiral resolution is obtained in 12.5 min with efficiencies greater than 200,000 theoretical plates using BSA as an additive, while no resolution is obtained in the absence of BSA. A general equation is derived to calculate the free energy of interaction between the leucovorin isomers and the BSA molecule. This method represents a new means of obtaining thermodynamic data for substrate binding interactions and for the general study of drug cross-reactions and interactions of drugs with serum and other proteins.
143 citations
TL;DR: Kinetic analysis indicates that the inhibitor interacted with the proteasome by a mechanism involving tight-binding, and may represent an important regulatory protein of this pathway of intracellular protein degradation.
TL;DR: It is reported that cor15 has potent cryoprotective activity in an in vitro Cryoprotection assay, and was very effective in protecting the cold-labile enzyme lactate dehydrogenase against freeze-inactivation.
TL;DR: The energetic cost of protein synthesis in terms of moles of adenosine triphosphate per gram ofprotein synthesis decreased with increasing rates of protein synthesisation at higher temperatures, suggesting that the energetic cost consists of a fixed and a variable component.
Abstract: To establish the energetic cost of protein synthesis, isolated trout hepatocytes were used to measure protein synthesis and respiration simultaneously at a variety of temperatures. The presence of bovine serum albumin was essential for the viability of isolated hepatocytes during isolation, but, in order to measure protein synthesis rates, oxygen consumption rates and RNA-to-protein ratios, BSA had to be washed from the cells. Isolated hepatocytes were found to be capable of protein synthesis and oxygen consumption at constant rates over a wide range of oxygen tension. Cycloheximide was used to inhibit protein synthesis. Isolated hepatocytes used on average 79.7±9.5% of their total oxygen consumption on cycloheximide-sensitive protein synthesis and 2.8±2.8% on maintaining ouabain-sensitive Na+/K+-ATPase activity. The energetic cost of protein synthesis in terms of moles of adenosine triphosphate per gram of protein synthesis decreased with increasing rates of protein synthesis at higher temperatures. It is suggested that the energetic cost consists of a fixed (independent of synthesis rate) and a variable component (dependent on synthesis rate).
TL;DR: In this article, the concentration dependence of surface tension was evaluated with DuNouy ring tensiometry for solutions of α-lactalbumin (α-Lac), β-Lactoglobulin (β-Lg), and bovine serum albumin (BSA).
TL;DR: The results suggest that the 53-kDa major surface protein of T. denticola may play a role in the attachment to host proteins and may thus be an important virulence determinant of this species.
Abstract: Treponema denticola surface proteins were studied for their biochemical and biological characteristics. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of detergent extracts of whole cells revealed a major protein of 53 kDa and a number of minor proteins. Antiserum raised against whole cells of T. denticola ATCC 35405 reacted with the 53-kDa protein and a 72-kDa protein but not with the other proteins. Immunoelectron microscopy with anti-53-kDa-protein antibodies showed that the 53-kDa protein is located on the surface of the cell. SDS-PAGE analysis of unheated samples indicated that the 53-kDa protein is the major component of oligomers with molecular masses ranging from 130 to 300 kDa. Western blot (immunoblot) analysis showed that the high-molecular-mass oligomers reacted with whole-cell antiserum and anti-53-kDa-protein antibody. The aggregates dissociated into their subunits after heating to 70 degrees C. Isoelectric focusing followed by SDS-PAGE indicated that the 53-kDa protein was separated into several forms with apparent pI values ranging from 8.0 to 5.5. The oligomeric forms were highly resistant to proteolysis by trypsin and proteinase K, whereas the monomeric proteins were readily digested. A clone expressing a 53-kDa antigen in Escherichia coli was isolated from a lambda ZAP II DNA library of T. denticola ATCC 35405. The recombinant protein had exactly the same molecular mass as the major 53-kDa T. denticola surface protein and reacted with antisera raised against this protein. The role of T. denticola ATCC 35405 surface proteins in attachment to laminin, fibronectin, gelatin, fibrinogen, and bovine serum albumin (BSA) was studied by a modified Western blot binding assay. Fibronectin, laminin, and fibrinogen attached to the 53-kDa surface protein of T. denticola as well as to a 72-kDa protein, whereas no attachment to gelatin or BSA was observed. Attachment could be inhibited by pretreating the blots with fibrinogen but not with gelatin or BSA. Our results suggest that the 53-kDa major surface protein of T. denticola may play a role in the attachment to host proteins and may thus be an important virulence determinant of this species.
TL;DR: The CD spectrum changes upon adsorption were significant in the “soft” protein molecules (myoglobin, hemoglobin, and BSA), while they were insingnificant in the“rigid” proteins (RNase A and peroxidase).
Abstract: The conformational changes in well-characterized model proteins [bovine ribonuclease A (RNase A), horseradish peroxidase, sperm-whole myoglobin, human hemoglobin, and bovine serum albumin (BSA)] upon adsorption on ultrafine polystyrene (PS) particles have been studied using circular dichroism (CD) spectroscopy. These proteins were chosen with special attention to molecular flexibility. The ultrafine PS particles were negatively charged and have average diameters of 20 or 30 nm. Utilization of these ultrafine PS particles makes it possible to apply the CD technique to determine the secondary structure of proteins adsorbed on the PS surface. Effects of protein properties and adsorption conditions on the extent of the changes in the secondary structure of protein molecules upon adsorption on ultrafine PS particles were studied. The CD spectrum changes upon adsorption were significant in the "soft" protein molecules (myoglobin, hemoglobin, and BSA), while they were insignificant in the "rigid" proteins (RNase A and peroxidase). The soft proteins sustained a marked decrease in alpha-helix content upon adsorption. Moreover, the native alpha-helix content, which is given as the percentage of the alpha-helix content in the free proteins, of adsorbed BSA was found to decrease with decreasing pH and increase with increasing adsorbed amount. These observations confirm some well-known hypotheses for the confirmational charges in protein molecules upon adsorption.
TL;DR: A blue fluorophore was isolated from human eye lens crystallins and it is likely that ASA is the major precursor of LM-1, since ASA concentration is unusually high in lens and has been found to be a powerful glycating agent of crystallins.
TL;DR: The strategic location of IRBP in the interphotoreceptor matrix (IPM) and its retinoid-binding ability make it a candidate for a role in 11-cis-RAL release, and high-performance liquid chromatography demonstrated that it was optimally released into the apical medium when apo-IRBP was present.
Abstract: This study investigates whether the interphotoreceptor retinoid-binding protein (IRBP) is necessary for the release of 11-cis-retinaldehyde (RAL) or if the retinoid is constitutively released from the retinal pigment epithelium (RPE) following synthesis. The strategic location of IRBP in the interphotoreceptor matrix (IPM) and its retinoid-binding ability make it a candidate for a role in 11-cis-RAL release. Fetal bovine RPE cells were grown in permeable chambers, and their apical surfaces were incubated with medium containing either apo-IRBP, the apo form of cellular retinaldehyde-binding protein (CRALBP), the apo form of serum retinol-binding protein (RBP), or bovine serum albumin (BSA) or with medium devoid of binding proteins. [3H]-all-trans-Retinol (ROL) was delivered to the basal surface of the cells by RBP. High-performance liquid chromatography demonstrated that [3H]-11-cis-RAL was optimally released into the apical medium when apo-IRBP was present. The most surprising result was the diminished level of [3H]-11-cis-RAL when apo-CRALBP was in the apical medium. Circular dichroism demonstrated that CRALBP had not been denatured by the photobleaching required for endogenous ligand removal. Therefore, apo-CRALBP should have been able to bind [3H]-11-cis-RAL if it was constitutively released into the apical medium. In addition, when proteins other than apo-IRBP were present, or if the cells were incubated with medium alone, the observed decrease in apical [3H]-11-cis-RAL was concomitant with a buildup of intracellular [3H]-all-trans-retinyl palmitate and [3H]-all-trans-ROL in the basal culture medium.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: For the H3-subtype virus A/Memphis/1/71 x A/Bel/42 (H3N1), sensitivity to beta inhibitors was determined by the oligosaccharide at residue 165 of the hemagglutinin, this glycosylation site being lost in a resistant mutant selected by growth in the presence of bovine serum as discussed by the authors.
Abstract: Normal bovine and mouse sera contain a component, termed beta inhibitor, that inhibits the infectivity and hemagglutinating activity of influenza A viruses of the H1 and H3 subtypes. We have previously shown these beta inhibitors to be mannose-binding lectins that apparently act by binding to carbohydrate on the viral hemagglutinin, blocking access of the receptor-binding site to receptors on host cells (E. M. Anders, C. A. Hartley, and D. C. Jackson, Proc. Natl. Acad. Sci. USA 87:4485-4489, 1990). For the H3-subtype virus A/Memphis/1/71 x A/Bel/42 (H3N1), sensitivity to beta inhibitors is determined by the oligosaccharide at residue 165 of the hemagglutinin, this glycosylation site being lost in a resistant mutant selected by growth in the presence of bovine serum. In the present study, we sequenced the hemagglutinin genes of additional bovine serum-resistant mutants derived from influenza viruses A/Philippines/2/82 (H3N2) and A/Brazil/11/78 (H1N1). The results confirm the importance of carbohydrate at residue 165 for inhibitor sensitivity of H3 viruses and implicate carbohydrate at residue 87 (94a in the H3 numbering system) as an important determinant in the sensitivity of H1-subtype viruses to the bovine inhibitor. Unlike the two H3 mutants, which had also gained resistance to hemagglutination inhibition by mouse serum, the H1 bovine serum-resistant mutant remained sensitive to the mouse beta inhibitor, suggesting that inhibition by the two types of sera is mediated by distinct mannose-binding lectins. In support of this hypothesis, the beta inhibitors in bovine and mouse sera were shown to differ in their pattern of inhibition by monosaccharides and in their sensitivity to 2-mercaptoethanol. In these and other properties, the bovine inhibitor closely resembled conglutinin, a Ca(2+)-dependent N-acetylglucosamine- and mannose-binding lectin present in bovine serum but absent from the serum of other species. Furthermore, polyclonal and monoclonal anticonglutinin antibodies abrogated the hemagglutination-inhibiting activity of bovine serum. Direct binding of conglutinin to the parent viruses and reduced binding to their respective mutants were confirmed by radioimmunoassay.
TL;DR: In this article, the diffusion coefficient of bovine serum albumin (BSA) was measured in aqueous solutions of varying temperature, pH, BSA concentration, and ionic strength.
Abstract: The diffusion coefficient of bovine serum albumin (BSA) was measured in aqueous solutions of varying temperature, pH, BSA concentration, and ionic strength. The measurements were carried out using dynamic light scattering with the photon detector set at a 90 o angle. The measured diffusion coefficients were compared to calculated values using phenomenological models which account for the screened Coulomb interaction between the charged proteins, as well as hydrodynamic corrections to the friction factor. The dimensions of BSA were obtained from structural data, and the charge on the protein was estimated using titration data
Patent•
20 Feb 1992TL;DR: In this paper, an improved surface erodible controlled release composition and the manufacturing thereof for the continuous administration of biologically active proteins or peptide fragments, is described, where the biologically active protein is dissolved in water or a suitable solvent, alone or in combination with stabilizing agents.
Abstract: An improved surface erodible controlled release composition and the manufacturing thereof, for the continuous administration of biologically active proteins or peptide fragments, is described. The biologically active protein is dissolved in water or a suitable solvent, alone or in combination with stabilizing agents. The solution is either lyophilized or spray dried to obtain a free flowing powder. The powder is then sieved to obtain the desired average particle size. The free flowing powder of the protein or the stabilized protein is then incorporated into a biodegradable matrix formed of fatty acid anhydride, fatty acid and/or a salt thereof. Examples using growth hormone and bovine serum albumin demonstrate enhanced release, stability and controlled release properties for the fatty acid anhydride microparticular system.
TL;DR: This study tested the effect of incorporating bovine serum albumin into the medium of hamster 2-cell embryos in vitro using a simple proteinfree, chemically defined medium generically designated Hamster Embryo Culture Medium.
Abstract: Dear Editor: In recent years, much emphasis has been placed on eliminating serum from culture media for somatic cells and preimplantation embryos, in part because of the high cost and inconsistency of this product, and in part to examine effects of specific growth factors and hormones without experiments being compromised by serum factors (3). In many studies, serum has been replaced with bovine serum albumin (BSA) (8,14). However, serum albumin, in general, binds biological substances such as fatty acids, steroids and many trace metals, provides an accessible protein reserve, serves as a colloid osmotic regulator and acts as a transport protein (1). Thus, BSA is not an inert constituent of culture media and may provide low molecular weight growth-promoting factors (9) as well as chelate heavy metals and other potentially toxic contaminants (4,7,10). Considerable progress has been made in supporting development of hamster preimplantation embryos in vitro using a simple proteinfree, chemically defined medium generically designated Hamster Embryo Culture Medium (HECM), from 0% 2-cell embryo development a few years ago (12) to approximately 50% blastocysts currently (11). However, this culture medium may lack important factors found in vivo that could improve development; accordingly, we examined the effect of incorporating bovine serum albumin into the medium. We tested the effect of four Fraction V BSA preparations on the development of hamster 2-cell embryos in vitro. Hamster 2-cell embryos, collected 32 h post egg-activation from PMSG-stimulated females mated to fertile males (13), were cultured in 100 #1 drops of HECM1 (13) containing 0.1 mg/ml polyvinyl alcohol (PVA) under a silicone oil overlay in an atmosphere of 10% CO2:10% 02:80% N 2 at 37.5 ° C for 72 h (11). The experiment consisted of five treatments, arranged as five drops of media in a 60 mm petri dish. The control treatment contained no BSA, while the four experimental treatments each contained a different batch of commercial Fraction V BSA at 3 mg/ml. BSA-1, BSA-2 and BSA-3 were obtained from Sigma Chemical Co., all purchased under catalog number A-9647, with lot numbers 41-F-0593, 106-F-0580 and 26-F-0202, respectively. BSA-4 was obtained from Armour Pharmaceuticals: catalog number 0140-00, lot number B-10012. The experiment was repeated four times. Embryo development, expressed as a percentage of the total number of embryos in each treatment, was determined at 48 h. The number of embryos that developed to the hatching blastocyst stage was recorded at 72 h. Transformed data were subjected to a 2-way ANOVA. F values were determined, and when they were significant, levels of treatments were compared using Newman-Keuls multiple range test. The four lots of BSA were examined using one-dimensional polyacrylamide gel electrophoresis. In the control treatment, containing no BSA, 49% of the 2-cell embryos cultured developed to the blastocyst stage; 14% were
TL;DR: Results demonstrate that, whereas MDP preferentially stimulates IgG1 antibodies, liposomes elicit high levels of IgG2a/2b isotypes with significantly longer serum half-lives, especially when MDP-GDP was present in the liposome.
TL;DR: Poly-β-hydroxybutyrate, an amphiphilic lipid that has been found to be a ubiquitous component of the cellular membranes of bacteria, plants and animals, is investigated using chemical and immunological methods and suggests it may have important physiological effects.
TL;DR: HepG2 cells were employed as model system to investigate potential relationships between early protein processing and Ca2+ storage by the endoplasmic reticulum and suppression of amino acid incorporation into total cellular proteins of HepG1 cells accompanied inhibitions of protein processing by agents depleting sequestered Ca2+, by dithiothreitol.
TL;DR: In this article, the effects of bovine somatotropin (bST) on specific high affinity binding proteins (IGFBPs) that modulate physiological responses to both IGF-I and IGF-II were determined.
Abstract: The insulin-like growth factors (IGF) circulate bound to specific high affinity binding proteins (IGFBPs) that modulate physiological responses to both IGF-I and IGF-II. Administration of bovine somatotropin (bST) to lactating cows has been shown to increase total serum levels of IGF-I; however, its effects on IGFBPs are unknown. Therefore, we determined the effects of bST on specific IGFBPs that are present in bovine serum and lymph. The results show that bovine serum contains IGFBPs with mol wt (Mr) estimates of 43,000, 39,000, 34,000, 29,000, and 24,000, as determined by ligand blotting. Using specific antisera, immunoblotting showed that the 43,000 and 39,000 Mr bands were IGFBP-3 and the 34,000 Mr band was IGFBP-2. All five forms of IGFBP were also present in afferent mammary lymph. To determine the effect of bST, four cows were treated with bST (40 mg/day) or vehicle for 12-day periods using a cross-over design. The intensity of the IGFBP-3 band increased 3.3 +/- 0.1-fold (mean +/- SE; P less than 0...
TL;DR: The serum-type mannose-binding protein is a defense molecule that has carbohydrate-dependent bactericidal effects but does not manifest any significant affinity enhancement toward small, di- and trivalent ligands, in contrast to the hepatic lectins whose affinity toward divalent ligands of comparable structures increased from 100- to 1000-fold.
TL;DR: In this article, the emulsifying behavior of covalent Maillard complexes of the non-ionic polysaccharide dextran with three proteins (11S globulin Vicia faba, bovine serum albumin, β-casein) has been investigated as a function of the molecular weight of the dextrans (4 · 10 4 or 5 · 10 5 Da) and the polysac-charide/protein molar ratio R.
TL;DR: Results indicate that trivalent Cr creates DNA protein crosslinks by binding with reactive amino acids and linking these to the phosphate backbone of DNA.
Abstract: Previous studies have examined Cr(III), or CrO4 reduced to Cr(III), binding in vitro to DNA. However, there have been few studies examining chromate binding to DNA in intact cells. Treatment of intact cells with chromate (Na2(51)CrO4) resulted in chromium (Cr) binding to DNA. The binding of Cr to DNA was much more stable when more residual peptide/amino acids were associated with DNA. A substantial portion of the Cr bound to DNA was released by treatment with EDTA, suggesting that trivalent Cr was the major oxidation state of Cr bound to DNA. Cr(III) stimulated the formation of amino acid-DNA and protein-DNA complexes in vitro. Tyrosine and cysteine exhibited the highest activity in being complexed to DNA by Cr(III) in vitro, while histidine, methionine and threonine also exhibited more activity than any other amino acid. Similar results were found in intact cells. The activity of proteins complexed to DNA by trivalent Cr depended upon the content of these reactive amino acids. Thus, bovine serum albumin was more active than actin, which in turn was more active than histones. These and other studies presented suggested that Cr(III) was involved directly in the formation of DNA-protein complexes in intact cells, unlike other metals such as Ni(II), which are thought to form DNA-protein cross-links catalytically and not participate directly in the complex. The majority of trivalent Cr associated with DNA was bound to the phosphate backbone without exhibiting any base specificity. Collectively, these results indicate that trivalent Cr creates DNA protein crosslinks by binding with reactive amino acids (i.e. cysteine, tyrosine or histidine) and linking these to the phosphate backbone of DNA.
TL;DR: Feedback regulation of albumin gene expression by serum colloids may serve as a specific homeostatic mechanism to maintain the steady-state level of total protein in the circulation.
Abstract: A novel feedback regulatory mechanism operating on transcription of the albumin gene is described in the rat. In 1946, it was proposed that circulating colloids, including serum albumin, may affect the synthesis and/or secretion of albumin in the liver. The molecular basis for this proposed regulation has now been investigated by adding oncotically active macromolecules to the circulation of normal or genetically albumin-deficient Nagase analbuminemic rats (NAR) and analyzing the hepatic expression of genes, including albumin after 24 h. The transcription rate of the albumin gene was higher in NAR than in normal rats and was dramatically reduced by raising serum albumin to 1.6 g/dl. Intravenous infusion of albumin into normal rats also decreased transcriptional activity of the albumin gene by 50-60%, and this decrease correlated with changes in serum colloid osmotic pressure after albumin infusion. Inhibition of albumin gene transcription was also observed upon intravenous infusion of other protein or nonprotein macromolecules, such as gamma-globulin and dextran. This down-regulation appears to control the steady-state level of albumin mRNA in the liver. Aside from a concomitant decrease in apo E gene transcription after albumin or macromolecule infusion, there was no change in the transcription rate of other genes, including those exhibiting liver-preferred or -specific expression (e.g., tyrosine amino-transferase, cytochrome P-450, alpha 1-antitrypsin, apolipoproteins A-I and B, and transferrin) or general cellular expression (e.g., alpha-tubulin, pro alpha 2 collagen, and beta-actin). Feedback regulation of albumin gene expression by serum colloids may serve as a specific homeostatic mechanism to maintain the steady-state level of total protein in the circulation.