Showing papers on "Myoglobin published in 1985"

Protein states and proteinquakes

Abstract: After photodissociation of carbon monoxide bound to myoglobin, the protein relaxes to the deoxy equilibrium structure in a quake-like motion Investigation of the proteinquake and of related intramolecular equilibrium motions shows that states and motions have a hierarchical glass-like structure

Blockade of endothelium-dependent and glyceryl trinitrate-induced relaxation of rabbit aorta by certain ferrous hemoproteins.

Abstract: We have reported previously that hemoglobin inhibits endothelium-dependent and glyceryl trinitrate-induced relaxation in the rabbit aorta. In this study we have examined the effects of other ferrous and ferric hemoproteins on endothelium-dependent and glyceryl trinitrate-induced relaxation to determine whether they also share the inhibitory properties of hemoglobin. Of the two ferrous hemoproteins tested, myoglobin (1-10 microM) abolished the endothelium-dependent relaxation induced by acetylcholine and produced a concentration-dependent reduction in the endothelium-independent relaxation induced by glyceryl trinitrate, in a manner similar to that reported previously for hemoglobin, but reduced cytochrome C was completely ineffective. The ferric hemoproteins methemoglobin (10 microM) and metmyoglobin (40 microM) produced only a slight inhibition of acetylcholine-induced relaxation. Methemoglobin (10 microM) also blocked only slightly the endothelium-dependent relaxation induced by the ionophore A23187 and had no effect on glyceryl trinitrate-induced relaxation. The inhibitory effects of these hemoproteins were reflected in their respective effects on the stimulation of cyclic GMP levels; thus, myoglobin (10 microM) inhibited the endothelium-dependent rise in cyclic GMP content induced by acetylcholine, as was found previously for hemoglobin, but methemoglobin (10 microM) was much less effective. The effectiveness of hemoglobin and myoglobin and the ineffectiveness of reduced cytochrome C in blocking the relaxations induced by acetylcholine and glyceryl trinitrate might suggest that only ferrous hemoproteins with ligand binding sites are inhibitory.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning, expression in Escherichia coli, and reconstitution of human myoglobin.

Abstract: A full-length cDNA clone for human myoglobin has been isolated from a human skeletal muscle cDNA library. The clone as isolated has a cDNA insert approximately one kilobase long and has 5' and 3' untranslated regions of approximately 80 and 530 base pairs, respectively. The sequence of the translated region corresponds exactly to that predicted for human myoglobin. The cDNA was expressed in high yield in Escherichia coli as a fusion protein consisting of the first 31 amino acids of the phage lambda cII gene, the tetrapeptide Ile-Glu-Gly-Arg, and the myoglobin sequence by following the approach of Nagai and Thogersen [Nagai, K. & Thogersen, M. C. (1984) Nature (London) 309, 810-812]. The fusion product was isolated, reconstituted with heme, cleaved with trypsin, and purified to generate a protein whose properties are indistinguishable from those for authentic human myoglobin. Myoglobin can be readily prepared on a gram scale by using these methods.

1H NMR characterization of metastable and equilibrium heme orientational heterogeneity in reconstituted and native human hemoglobin.

Abstract: A proton nuclear magnetic resonance study of the reaction of apohemoglobin A with both oxidized and reduced hemes reveals that at least two slowly interconverting species are initially formed, only one of which corresponds to the native proteins. Reconstitutions with isotope-labeled hemes reveal that the hyperfine-shift patterns for heme resonances in the metazido derivatives differ for the two species by interchange of heme environment characteristic of heme orientational disorder about the alpha, gamma-meso axis, as previously demonstrated for myoglobin [La Mar, G. N., Davis, N. L., Parish, D. W., & Smith, K. M. (1983) J. Mol. Biol. 168, 887-896]. Careful scrutiny of the 1H NMR spectrum of freshly prepared hemoglobin A (Hb A) reveals that characteristic resonances for the alternate heme orientation are present in both subunits, clearly demonstrating that "native" Hb A possesses an important structure heterogeneity. It is observed that this heterogeneity disappears with time for one subunit but remains unchanged in the other. This implies that a metastable disordered state in vivo involves the alpha subunit and an equilibrium disordered state both in vivo and in vitro is involved within the beta subunit. The presence of metastable disorder in fresh blood suggests an in vivo hemoglobin assembly from apoprotein and heme that is similar to the in vitro reconstitution process. The slow equilibration and known lifetimes for erythrocytes provide a rationalization for the presence of detectable metastable states. The implications of such heme disorder for Hb function are discussed.

Patterns of myoglobin release after reperfusion of injured myocardium.

Abstract: Myoglobin is an intracardiac protein that is released into the blood after myocardial injury and is then cleared rapidly by the kidneys. This study was undertaken to determine whether successful reperfusion of damaged myocardium could be assessed by examination of blood myoglobin concentration-time patterns. After release of a 2 hr occlusion of the mid left anterior descending coronary artery in 11 dogs that had been instrumented over the long term, immunoreactive arterial plasma concentration of myoglobin, [Mb], rose rapidly to a peak within 25 +/- 2(SEM) min (range 20 to 40). Individual peaks were three to 165 times the myoglobin levels immediately before release of the occlusion. Myoglobin was cleared rapidly from plasma, falling to one-half its peak level 38 +/- 3 min after the peak. Similarly well-defined peaks in [Mb] were evident in plasma from the great cardiac vein (GCV), with a mean time to peak of 16 +/- 2 min and a magnitude of two to 177 times prerelease values. In contrast, arterial and GCV creatine kinase activity-time curves showed less defined peaks and they occurred later and with more variability (60 to 330 min after reperfusion). In nine patients with acute infarction, successful coronary artery reopening was also accompanied by a sharp four- to sixteenfold rise in plasma [Mb] within 1 to 2 hr. Elevations in plasma creatine kinase were slower and more prolonged, peaking at 2 to 18 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxygen transport in rest-work transition illustrates new functions for myoglobin.

Abstract: Myoglobin (Mb) saturation was measured spectroscopically in 1,950 randomly selected cells from dog gracilis muscles frozen in situ during the transition from rest to steady twitch contraction at ap...

1H NMR study of labile proton exchange in the heme cavity as a probe for the potential ligand entry channel in myoglobin.

Abstract: The exchange rates of heme cavity histidine nitrogen-bound protons in horse and dog metcyanomyoglobins have been determined at 40 degrees C as a function of pH by 1H NMR spectroscopy. They were compared to the results reported for the sperm whale homologue [Cutnell, J. D., La Mar, G. N., & Kong, S. B. (1981) J. Am. Chem. Soc. 103, 3567-3572]. The rate profiles suggest that the exchange follows EX2-type kinetics, and the relative rate values favor a penetration model over a local unfolding model. It was found that the behavior of protons located on the proximal side of the heme is similar in the three proteins. The distal histidyl imidazole NH, however, shows a highly accelerated hydroxyl ion catalyzed rate in horse and dog myoglobins relative to that in sperm whale myoglobin. NMR spectral and relaxational characteristics of the assigned heme cavity protons indicate that the global geometry of the heme pocket is highly conserved in the ground-state structure of the three proteins. We propose a model that attributes the different distal histidine exchange behavior to the relative dynamic stability of the distal heme pocket in dog or horse myoglobin vs. sperm whale myoglobin. This model involves a dynamic equilibrium between a closed heme pocket as found in metaquomyoglobin [Takano, T. (1977) J. Mol. Biol. 110, 537-568] and an open pocket as found in phenylmetmyoglobin [Ringe, D., Petsko, G. A., Kerr, D. E., & Ortiz de Montellano, P. R. (1984) Biochemistry 23, 2-4].(ABSTRACT TRUNCATED AT 250 WORDS)

Nature of the FeO2 bonding in myoglobin: An overview from physical to clinical biochemistry

Abstract: The iron(II)-dioxygen bond in myoglobin and hemoglobin is a subject of wide interest. Studieas range from examinations of physical-chemical properties dependent on electronic structure, to investigations of stability as a function of oxygen supply. Stability properties are of particular importance in vivo, since the oxygenated form is known to be oxidized easily to the ferric form, which cannot be oxygenated and is therefore physiologically inactive. Kinetic and thermodynamic studies of the stability of native oxymyoglobin have revealed a new feature in FeO2 bonding. In vivo. the iron center is always subject to a nucleophilic attack of the water molecule or hydroxyl ion, which can enter the heme pocket from the surrounding solvent, and thereby irreversibly displace the bound dioxygen from MbO2 in the form of O 2 − so that the iron is converted to the ferric form. A free energy diagram for the potential reactions of FeO2 visualizes myoglobin as a molecular structure that can provide in solution the delicate balance of kinetic and thermodynamic factors necessary to stabilize reversible oxygenation, as opposed to irreversible autoxidation to metmyoglobin.

Inactivation of myoglobin by ortho-substituted arylhydrazines. Formation of prosthetic heme aryl-iron but not N-aryl adducts

Abstract: Stable phenyl-iron complexes are known to form in the reactions of myoglobin, hemoglobin, and catalase with phenylhydrazine. The phenyl moiety in these complexes migrates from the iron to a nitrogen of the porphyrin upon denaturation of the hemoproteins. Complexes obtained from myoglobin and ortho-substituted phenylhydrazines, however, are much less stable, have distinct chromophores, and do not yield N-arylporphyrins. These abnormal properties imply that the complexes differ in structure (e.g., they are aryldiazenyl-rather than aryl-iron complexes) or that ortho substitution strongly alters the chemistry of aryl-iron complexes. The present NMR studies unambiguously demonstrate that ortho-substituted phenylhydrazines give normal aryl-iron complexes but that the aryl group in these complexes is conformationally locked and is unable to shift from iron to nitrogen.

Myoglobin in the Very Early Phase of Acute Myocardial Infarction

Abstract: In this study of 35 patients with a definite or possible myocardial infarction seen within the first 5 h of the onset of symptoms and who could clearly define the onset of symptoms, the serum myoglobin was raised in 20% of those in whom blood was sampled within 1 h of the acute event. In 11 of the 35 (31%) patients the serum myoglobin was normal in the first blood sample. Of the nine patients seen within the first 2 h of the onset of symptoms who had frequent samples taken, the first raised serum myoglobin was recorded from 45 min to 3 h 15 min after the onset of symptoms. The serum levels started to rise 15-20 min before levels greater than 85 ng/mL were reached. In the absence of further chest pain more than one peak in serum myoglobin was recorded in 58% of the patients with acute myocardial infarction. The serum myoglobin level returned to normal within 24 h of the onset of symptoms in 44% of patients and within 36 h in 67%.

Relationship between the concentration of myoglobin and parvalbumin in various types of muscle tissues from chickens.

Abstract: The concentration of parvalbumin was determined in various types of chicken muscle by immunological analysis and was compared with that of myoglobin. Parvalbumin was present specifically in skeletal muscle and absent in cardiac and gizzard muscle; exceptionally, neither parvalbumin nor myoglobin was detected in white breast muscle. The wing and leg red muscles, which had larger amounts of myoglobin, contained smaller quantities of parvalbumin. In these muscles, the concentration of parvalbumin was inversely related to that of myoglobin (correlation coefficient = -0.69). Both myoglobin and parvalbumin were observed in the legs of 18-d-old embryos; the parvalbumin content exceeded that of myoglobin until the birds were 4 to 6 weeks old, but the relationship was reversed thereafter. Myoglobin in gizzard muscle was present in 18-d-old embryos and increased markedly at hatching; it was already present in cardiac muscle at an early embryonic stage, increasing gradually until 14 weeks after hatching.