Showing papers on "Myoglobin published in 2001"
TL;DR: Even an ordinary globular protein can assume a rogue guise if conditions are right and the molecule can be tricked into thinking it is another protein.
Abstract: Even an ordinary globular protein can assume a rogue guise if conditions are right.
780 citations
TL;DR: The biochemical basis underlying the effects of NO on cardiac function is outlined in this article, beginning with the idea that this gas is an inhibitor of cytochrome-c oxidase.
218 citations
TL;DR: Maurizio Brunori argues that myoglobin can also play the role of intracellular scavenger of nitric oxide, an inhibitor of mitochondrial cytochrome-c oxidase, thereby protecting respiration in the skeletal muscle and the heart.
185 citations
TL;DR: Results convey the general picture that pre‐existing internal cavities are involved in controlling the dynamics and reactivity of the reactions of Mb with O2 and other ligands, including NO.
Abstract: Small globular proteins contain internal cavities and packing defects that reduce thermodynamic stability but seem to play a role in controlling function by defining pathways for the diffusion of the ligand/substrate to the active site. In the case of myoglobin (Mb), a prototype for structure–function relationship studies, the photosensitivity of the adduct of the reduced protein with CO, O2 and NO allows events related to the migration of the ligand through the matrix to be followed. The crystal structures of intermediate states of wild-type (wt) and mutant Mbs show the photolysed CO to be located either in the distal heme pocket (primary docking site) or in one of two alternative cavities (secondary docking sites) corresponding to packing defects accessible to an atom of xenon. These results convey the general picture that pre-existing internal cavities are involved in controlling the dynamics and reactivity of the reactions of Mb with O2 and other ligands, including NO.
168 citations
TL;DR: This work has converted myoglobin into a peroxidase-like enzyme by alternation of the heme distal pocket via site-directed mutagenesis and has not observed an enhancement in the activation of peroxide by the proximal mutant with tyrosine, the exogenous phenolate, and benzoate.
Abstract: To pursue structure−function relationships of heme enzymes in the activation of peroxides, we have chosen to use myoglobin as the framework for our molecular engineering studies. Comparison of the crystal structures of myoglobin and peroxidases reveals differences in the arrangement of amino acid residues in heme active sites. On the basis of these structural differences and the reaction mechanisms of peroxidases, we have converted myoglobin into a peroxidase-like enzyme by alternation of the heme distal pocket via site-directed mutagenesis. The replacement of the proximal histidine with cysteine and the exogenous substituted imidazoles slightly accelerates the peroxide O−O bond cleavage due to the electron donor characteristics. However, we have not observed an enhancement in the activation of peroxide by the proximal mutant with tyrosine, the exogenous phenolate, and benzoate. A clear understanding of the absolute role of the proximal ligand remains elusive.
135 citations
TL;DR: Experimental data on site-directed mutants show that the main determinant of ligand affinity changes is the polarity of the binding pocket and that H-bonding by the distal histidine accounts for about 85% of the O(2)/CO discrimination while steric hindrance accounts for the remaining 15%.
Abstract: Early reports of a severely bent CO adduct in myoglobin inspired the idea that heme proteins discriminate against CO, relative to O2, via steric hindrance imposed by a distal histidine residue. Recent results showing that the bound CO is only slightly distorted do not by themselves overthrow the steric hypothesis, because the steric energy could be stored in displacements of the protein. However, experimental data on site-directed mutants show that the main determinant of ligand affinity changes is the polarity of the binding pocket and that H-bonding by the distal histidine accounts for about 85% of the O2/CO discrimination while steric hindrance accounts for the remaining 15%.
133 citations
TL;DR: It is shown that oxidative as well as non-oxidative mechanisms introduce carbonyl groups into proteins, providing a moiety for quantification with 2,4-dinitrophenylhydrazine (DNPH) and that heme-containing compounds may effect carbonyls quantification.
Abstract: The spectrophotometric protein carbonyl assay is used as an indicator of protein damage by free radical reactions in vitro and in a variety of pathologies. We investigated model proteins and a variety of oxidative and non-oxidative reactions, as well as what effects hemoglobin, myoglobin, and cytochrome c might have on levels of protein carbonyls. We show that oxidative as well as non-oxidative mechanisms introduce carbonyl groups into proteins, providing a moiety for quantification with 2,4-dinitrophenylhydrazine (DNPH). Bovine serum albumin exposed to oxidative scenarios, such as hypochlorous acid, peroxynitrite, and metal-catalyzed oxidation exhibited variable, but increased levels of carbonyls. Other non-oxidative modification systems, in which proteins are incubated with various aldehydes, such as malondialdehyde, acrolein, glycolaldehyde, and glyoxal also generated significant amounts of carbonyls. Furthermore, purified myoglobin, hemoglobin, and cytochrome c show high absorbance at the same wavelengths as DNPH. The high levels observed are due to the innate absorbance of hemoglobin, myoglobin, and cytochrome c near the assay spectra of DNPH. These studies show that carbonyl content could be due to oxidative as well as non-oxidative mechanisms and that heme-containing compounds may effect carbonyl quantification.
128 citations
TL;DR: The reaction products of myoglobin and simple phenolic compounds, with different configurations of hydroxyl groups, and p-quinone were characterized in terms of selected properties and by in vitro digestion and showed high reactivity leading to structural changes in myoglobin.
Abstract: The reaction products of myoglobin and simple phenolic compounds, with different configurations of hydroxyl groups, and p-quinone were characterized in terms of selected properties (electrophoretic, chromato- graphic and mass spectrometric) and by in vitro digestion. The o-, and p-hydroxyphenols, p-quinone and gallic acid showed high reactivity leading to structural changes in myoglobin. In comparison, ferulic acid and m-hydroxyphenol reacted to only a small extent, especially affecting tryptophan fluorescence of myoglobin. The enzymatic digestion (tryptic, a-chymotryptic, peptic and pancreatic), on the basis of in vitro experiments with derivatized myoglobin,
126 citations
TL;DR: It was found that when consumption is high enough to produce regions of hypoxia under steady flow conditions, vasomotion-induced flow oscillations can significantly increase tissue oxygenation and decrease oxygen transport heterogeneity, suggesting that in highly aerobic muscles short-term storage of oxygen is more important than the possibility of increasing transport through vasomotions.
107 citations
TL;DR: It is found conclusive evidence that Mb is important in facilitating O 2 diffusion from the vasculature to mitochondrial cytochromes and that the oxygen reservoir of myoglobin is of functional relevance in the beating mammalian heart.
Abstract: In this study, the hemodynamic effects of acute myoglobin (Mb) inhibition with CO on isolated hearts of wild-type (WT) mice were examined at different degrees of oxygenation. Hearts from myoglobin knockout (myo -/- ) mice served as appropriate controls. The intracellular MbO 2 dissociation curve, as measured by 1 H NMR, was determined by systematically lowering the O2 content of the perfusion medium. At 100% MbO2 saturation (buffer O2: 75%), complete inhibition of Mb with 20% CO did not alter left ventricular developed pressure (LVDP) or coronary venous PO2 (PvO2) and thus myocardial O2 consumption. At 87% MbO2 saturation (buffer O 2: 65%), CO applied to WT hearts significantly decreased LVDP by 12% and increased P vO2 by 30% (both P<0.005) respectively, whereas no effects were observed in myo -/- hearts. Cell width in isolated myo -/- as compared with WT cardiomyocytes was reduced (4.8 µm vs. 5.4 µm, P<0.001), whereas cell length did not differ. At ambient PO2 of 8 mm Hg, oxygen consumption of stimulated myo -/cardiomyocytes was only 60% that of WT controls (P<0.001). Our results do not support Mb-mediated oxidative phosphorylation in the beating mouse heart. However, we find conclusive evidence that Mb is important in facilitating O 2 diffusion from the vasculature to mitochondrial cytochromes and that the oxygen reservoir of myoglobin is of functional relevance in the beating mammalian heart.
105 citations
TL;DR: The results demonstrate that mammalian organisms are capable of a broad spectrum of adaptive responses that can compensate for a potentially serious defect in cellular oxygen transport.
Abstract: Myoglobin is a cytoplasmic hemoprotein that is restricted to cardiomyocytes and oxidative skeletal myofibers and facilitates oxygen delivery during periods of high metabolic demand. Myoglobin conte...
TL;DR: It is proposed that the protonated form of ferryl myoglobin (Fe(4+) - OH(-)) is the reactive species regulating the peroxidatic activity of myoglobin, making myoglobin considerably less reactive towards lipids and lipid hydroperoxides.
TL;DR: It is concluded that the heme "doming" mode is significantly delocalized, so that distant sites respond to oxygen binding on vibrational time scales, which has ramifications for understanding long-range interactions in biomolecules, such as those that mediate cooperativity in allosteric proteins.
Abstract: We report the complete vibrational spectrum of the probe nucleus 57Fe at the oxygen-binding site of the protein myoglobin. The Fe-pyrrole nitrogen stretching modes of the heme group, identified here, probe asymmetric interactions with the protein environment. Collective oscillations of the polypeptide, rather than localized heme vibrations, dominate the low frequency region. We conclude that the heme "doming" mode is significantly delocalized, so that distant sites respond to oxygen binding on vibrational time scales. This has ramifications for understanding long-range interactions in biomolecules, such as those that mediate cooperativity in allosteric proteins.
TL;DR: The data reveal that myoglobin is necessary to support cardiac function during development, but adaptive responses evoked in some animals can fully compensate for the defect in cellular oxygen transport resulting from the loss of myoglobin.
Abstract: —Mice lacking myoglobin survive to adulthood and meet the circulatory demands of exercise and pregnancy without cardiac decompensation. In the present study, we show that many myoglobin-deficient embryos die in utero at midgestation with signs of cardiac failure. Fetal mice that survive to gestational day 12.5, however, suffer no subsequent excess mortality. Survival in the absence of myoglobin is associated with increased vascularity and the induction of genes encoding the hypoxia-inducible transcription factors 1α and 2, stress proteins such as heat shock protein 27, and vascular endothelial growth factor. These adaptations are evident in late fetal life, persist into adulthood, and are sufficient to maintain normal myocardial oxygen consumption during stressed conditions. These data reveal that myoglobin is necessary to support cardiac function during development, but adaptive responses evoked in some animals can fully compensate for the defect in cellular oxygen transport resulting from the loss of myoglobin.
TL;DR: In this article, the radial diffusivities of myoglobin and other proteins in single skeletal and cardiac muscle cells were measured using a fluorescence recovery after photobleaching (FRAP) technique.
Abstract: We have used a fluorescence recovery after photobleaching (FRAP) technique to measure radial diffusion of myoglobin and other proteins in single skeletal and cardiac muscle cells. We compare the radial diffusivities, Dr (i.e., diffusion perpendicular to the long fiber axis), with longitudinal ones, Dl (i.e., parallel to the long fiber axis), both measured by the same technique, for myoglobin (17 kDa), lactalbumin (14 kDa), and ovalbumin (45 kDa). At 22°C, Dl for myoglobin is 1.2 × 10−7 cm2/s in soleus fibers and 1.1 × 10−7 cm2/s in cardiomyocytes. Dl for lactalbumin is similar in both cell types. Dr for myoglobin is 1.2 × 10−7 cm2/s in soleus fibers and 1.1 × 10−7 cm2/s in cardiomyocytes and, again, similar for lactalbumin. Dl and Dr for ovalbumin are 0.5 × 10−7 cm2/s. In the case of myoglobin, both Dl and Dr at 37°C are about 80% higher than at 22°C. We conclude that intracellular diffusivity of myoglobin and other proteins (i) is very low in striated muscle cells, ≈1/10 of the value in dilute protein solution, (ii) is not markedly different in longitudinal and radial direction, and (iii) is identical in heart and skeletal muscle. A Krogh cylinder model calculation holding for steady-state tissue oxygenation predicts that, based on these myoglobin diffusivities, myoglobin-facilitated oxygen diffusion contributes 4% to the overall intracellular oxygen transport of maximally exercising skeletal muscle and less than 2% to that of heart under conditions of high work load.
TL;DR: Because the oxygen affinity of Mb decreases with increasing temperature, the above differences in oxygen affinity between endothermic and ectothermic fish are reduced when adjusted for the in vivo muscle temperature of the animal.
Abstract: Myoglobin (Mb) buffers intracellular O2 and facilitates diffusion of O2 through the cell. These functions of Mb will be most effective when intracellular Po 2 is near the partial pressure of oxygen...
TL;DR: Data indicate that the reaction of wild-type human Mb and NO yields either heme-NO or a novelS-nitrosated protein dependent on the oxidation state of the heme iron and the presence or absence of dioxygen.
TL;DR: The present results indicate that the buffer-perfused guinea pig heart at 37 degrees C has an intracellular oxygen tension just above the threshold for impaired function.
Abstract: Critical intracellular myocardial oxygen tension was determined by optical spectroscopic measurement of myoglobin oxygen saturation in crystalloid-perfused guinea pig hearts. Accurate end-point det...
TL;DR: In this paper, the autocorrelation function of vibrational frequency fluctuations of the CO ligand in carbonmonoxy myoglobin, C‰‰(t), was computed from molecular dynamics simulations.
Abstract: The autocorrelation function of vibrational frequency fluctuations of the CO ligand in carbonmonoxy myoglobin, C‰‰(t), is computed from molecular dynamics simulations. Electrostatic interactions are assumed to dominate the modulation of the CO vibrational frequency. The simulated C‰‰(t) is consistent with linear and nonlinear infrared spectroscopic measurements. The short-time decay of C‰‰ is dominated by dynamics of the distal histidine, and of a water molecule that can occupy the heme pocket. Correlated protein and solvent dynamics induce spectral diffusion of the CO frequency on longer time scales.
TL;DR: Mutational analysis confirms the importance of A/T-rich, MEF2-binding motifs in myoglobin gene regulation, and demonstrates a previously unsuspected role for an intragenic E-box motif as a negative regulatory element contributing to the tightly regulated variation inMyoglobin gene expression among particular myofiber subtypes.
TL;DR: This overview represents a compendium for the molecular mechanism of autoxidation for myoglobin and hemoglobin molecules with special emphasis on the possible roles of the distal histidine.
Abstract: The reversible and stable binding of dioxygen to the heme iron (II) is the basis of myoglobin and hemoglobin functions. During reversible oxygen binding, however, the oxygenated form of myoglobin or hemoglobin is oxidized easily to the ferric (III) met-form with generation of the superoxide anion. Thus, stability property of each oxygenated form is of particular importance in vivo, since the iron (III) species cannot bind dioxygen and is therefore physiologically inactive. With special emphasis on the possible roles of the distal histidine, this overview represents a compendium for the molecular mechanism of autoxidation for myoglobin and hemoglobin molecules.
TL;DR: The results show that myoglobin is not homogeneously distributed in the locomotory muscle of cetaceans and that levels may be highest in those areas that produce greater force and consume more oxygen during aerobic swimming.
Abstract: Myoglobin is an important storage site for oxygen in the swimming muscles of diving marine mammals. However, little is known about its distribution within muscles since previous studies have relied on single samples. The goal of this study was to determine the distribution of myoglobin within the swimming muscles of five species of cetacean: dusky dolphin, false killer whale, striped dolphin, humpbacked dolphin and bottlenose dolphin. The entire dorsal (epaxial) and ventral (hypaxial) swimming muscles were removed from each animal and weighed. Transverse sections were taken from the cranial, middle and caudal regions of each muscle and sampled along a circular grid with a minimum of 30 sites per section. Spectrophotometric analysis was used to measure the myoglobin concentration of each sample. Contour maps of myoglobin concentration were made for each transverse section. Myoglobin concentration was found to be non-uniformly distributed within the muscle. The interior of the muscle lying closest to the vertebrae showed a significantly higher (11 %) mean myoglobin concentration than the exterior of the muscle for all five species. In the epaxial muscles, the mean myoglobin concentration was significantly higher in the caudal region closest to the flukes. The two deep-water species (false killer whale and striped dolphin) had significantly higher myoglobin concentrations than the three species (dusky, humpbacked and bottlenose dolphins) that occur in shallow, coastal waters. These results show that myoglobin is not homogeneously distributed in the locomotory muscle of cetaceans and that levels may be highest in those areas that produce greater force and consume more oxygen during aerobic swimming. Enhancing oxygen stores in those areas of the muscle that work the hardest would theoretically lengthen the aerobic dive limit of the animal during submerged swimming.
TL;DR: A pair of well-defined redox waves of myoglobin at a DL-homocysteine self-assembled gold electrode was achieved and X-ray photoelectron spectroscopy measurements demonstrated that Hcy monolayer was formed and Mb was bound to Hcymonolayer.
TL;DR: The data suggest that the acidic pH and low oxygen tension produced during myocardial ischemia will facilitate myoglobin-catalyzed, peroxyntrite-independent formation of 3-nitrotyrosine.
TL;DR: It is found that estimation of myocardial damage through cardiac markers levels in serum depends on the site of injury (atrium or ventricle) and comparison of my cardiac injury among individuals using marker levels in Serum is not reliable because of the varied ranges of markers in tissue contents.
Abstract: We studied the content and distribution of heart-specific markers troponin I and troponin T in relation to conventional non-heart specific myoglobin and alpha-hydroxybutyric acid dehydrogenase (HBD) in the hearts of 34 patients who died of various causes. Tissue was obtained from the right and left ventricles, the interventricular septum, and the right and left atria. We found significant differences in the contents expressed per gram wet weight tissue in the right and left ventricles for troponin I (by 1 of the 2 methods used), troponin T, myoglobin, and HBD and no differences per gram of protein. The biochemical contents per gram wet weight tissue and per gram protein were significantly lower in the right and left atria for all studied markers compared with the right and left ventricles. No significant differences were found in biochemical contents between the right and left atria. These findings imply that estimation of myocardial damage through cardiac markers levels in serum depends on the site of injury (atrium or ventricle). Comparison of myocardial injury among individuals using marker levels in serum is not reliable because of the varied ranges of markers in tissue contents.
TL;DR: It was suggested that high post-mortem urinary myoglobin levels in acute and subacute death cases may be a possible indicator of antemortem massive skeletal muscle damage as well as exertional muscle hyperactivity or convulsive disorders associated with hypoxia.
TL;DR: The results clearly point to the important role of electrostatic interactions on the gas phase stability of noncovalent complexes and therefore the ion signals observed in ESI-MS experiments.