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PubMed1997

Rapid myoglobin analysis to assess coronary artery reperfusion after acute myocardial infarction.

BACKGROUND: Coronary artery reperfusion significantly improves outcome in patients with acute myocardial infarction. A noninvasive method for assessing reperfusion in the early stage of infarction should be helpful in patient management. HYPOTHESIS: We sought to assess whether release pattern of myoglobin is helpful in identifying patients with and without reperfusion following thrombolytic therapy for myocardial infarction. METHODS: Myoglobin was measured before thrombolysis, half hourly for 4 h, then every 2 h for 10 h. Myoglobin was analyzed using a ward-based "rapid" and automated analyzer that yielded quantitative results within 10 min of blood collection. RESULTS: In the 15 patients with coronary reperfusion, the time from thrombolysis to peak myoglobin levels (mean +/- SD, 2.4 +/- 1.5 h) was significantly lower than in nonreperfused patients (5.1 +/- 2.9, p < 0.01). As an indicator for reperfusion, a doubling of myoglobin 1 h after streptokinase achieved a sensitivity of 80%, a specificity of 80%, and a predictive accuracy of 80%. CONCLUSIONS: The difference in myoglobin release kinetics is useful in identifying patients without coronary reperfusion and should aid in their management.

Biomarkers↗
PubMed1988

T cell response to myoglobin: a comparison of T cell clones in high-responder and low-responder mice.

Mice carrying the H-2b haplotype (e.g., inbred strains C57BL/6 and C57BL/10) are low responders to sperm whale myoglobin when tested in the T cell proliferation assay. Their response is improved by the removal of the Ly-2+ cells from the lymph node population, but it still remains significantly lower than that of cells cells from high-responder strains (e.g., DBA/2, H-2d). To determine whether T cells from the low and high-responder mice recognize the same or different epitopes on the immunizing antigen, we obtained sets of T cell clones from both strains and tested them against peptides representing different regions of the myoglobin molecule, as well as against myoglobins from species other than the sperm whale. Four types of T cell clones were obtained from the DBA/2 mice: 3 types responded to the peptide 107-120 (9 clones altogether), and 1 type responded to the peptide 133-149 (4 clones altogether). The 3 types responding to the peptide 107-120 could be distinguished by their response to horse myoglobin or by the restriction of the response (Ad vs. Ed). Similarly, 5 types of T cell clones were obtained from the C57BL/6 mice: 2 types responded to the peptide 10-22 (1 type, but not the other, responded to horse myoglobin); 1 type responded to the peptide 133-149; and 2 types did not respond to any of the peptides used (1 type, but not the other, responded to dog myoglobin). All 5 types (13 clones altogether) were presumably Ab restricted. These results demonstrate the diversity of epitopes in single antigenic regions and show equivalent heterogeneity of T cell repertoires in high and low responder mice. Attempts to demonstrate specific T cell suppression in the low responder mice failed; only partial, nonspecific suppression was observed.

Animals↗
PubMed1991

Antigen processing by endosomal proteases determines which sites of sperm-whale myoglobin are eventually recognized by T cells.

This study reports an identification of the major processing products of an exogenous protein antigen, viz, sperm-whale myoglobin, as obtained after cell-free processing with partially purified macrophage endosomes. It is demonstrated that such a system yields fragments that are indistinguishable by high performance liquid chromatography analysis from those generated after uptake of myoglobin inside live macrophages. The concerted action of the endosomal proteases cathepsin D and cathepsin B can account for nearly all cleavages observed. Cathepsin D appears to be mainly responsible for the initial cleavage of myoglobin, while cathepsin B catalyzes the C-terminal trimming of initially released fragments. The fragments released by cathepsin D contain most, if not all, major epitopes for murine myoglobin-specific helper T cells. Interestingly, each known T cell epitope of myoglobin is located at the very N terminus of a different myoglobin fragment released upon processing. In order to explain this correspondence, noted also in several other protein antigens, a structural relationship is proposed between antigen processing by cathepsin D and antigen recognition by major histocompatibility complex (MHC) class II products. As is demonstrated here, this relationship may be used as a predictive tool for the identification of MHC-binding sequences as well as of T cell epitopes in their naturally occurring form.

Amino Acid Sequence↗
PubMed1992

Measurement of serum myoglobin by a turbidimetric latex agglutination method.

We evaluated an immunoturbidimetric quantitation for serum myoglobin by the latex agglutination method using an automated biochemical analyzer. This method is rapid, specific, accurate, precise, and has wide dynamic range. The total assay time is 10 min and is performed at 37 degrees C with continuous monitoring at 570 nm. The assay results were compared with radioisotopic immunoassay results and showed a good correlation coefficient, r = 0.99; Y = 0.98 x + 9.3; N = 79. Sera from healthy adults has a myoglobin concentration in the range of 15-80 ng/ml(N = 362). Sex- and age-related differences were observed. The serum myoglobin levels in males and elderly people showed higher concentration than in females and younger people. The peak elevation of serum myoglobin compared with other cardiac markers was observed within 6 hours after onset of chest pain as well as the CK-isoform ratio (MM3/MM1). All of the serum from 21 patients with definite acute myocardial infarction showed increased serum myoglobin levels (100-1200 ng/ml) upon admission and within 6 hours. The results suggest that assays for serum myoglobin levels are helpful in the early diagnosis of acute myocardial necrosis.

Adolescent↗
PubMed1992

Development of a rapid microparticle-enhanced nephelometric immunoassay for serum myoglobin in acute myocardial infarction.

A microparticle-enhanced nephelometric immunoassay was developed for myoglobin quantitation in human serum. It uses rabbit antimyoglobin serum and hydrophilic polyacrylic microparticles covalently coated with baboon myoglobin in a competitive immunoagglutination system. The level of microparticle agglutination is assessed with a specially designed nephelometer. This sensitive (45 ng/ml of myoglobin detected in serum) and accurate (coefficients of variation from 3.0% to 8.2% in precision study and linear recovery of myoglobin in overloaded sera) immunoassay was evaluated with human sera from patients suffering from acute myocardial infarction. Myoglobin levels in patient's serum on admission appeared to be correlated with clinical and biological parameters assessed in emergency wards and later. This new, rapid, and easy microparticle-enhanced nephelometric immunoassay could thus be useful in emergency conditions for the early quantitation of serum myoglobin.

Adult↗
PubMed1997

Folding propensities of peptide fragments of myoglobin.

Myoglobin has been studied extensively as a paradigm for protein folding. As part of an ongoing study of potential folding initiation sites in myoglobin, we have synthetized a series of peptides covering the entire sequence of sperm whale myoglobin. We report here on the conformation preferences of a series of peptides that cover the region from the A helix to the FG turn. Structural propensities were determined using circular dichroism and nuclear magnetic resonance spectroscopy in aqueous solution, trifluoroethanol, and methanol. Peptides corresponding to helical regions in the native protein, namely the B, C, D, and E helices, populate the alpha region of (phi, psi) space in water solution but show no measurable helix formation except in the presence of trifluoroethanol. The F-helix sequence has a much lower propensity to populate helical conformations even in TFE. Despite several attempts, we were not successful in synthesizing a peptide corresponding to the A-helix region that was soluble in water. A peptide termed the AB domain was constructed spanning the A- and B-helix sequences. The AB domain is not soluble in water, but shows extensive helix formation throughout the peptide when dissolved in methanol, with a break in the helix at a site close to the A-B helix junction in the intact folded myoglobin protein. With the exception of one local preference for a turn conformation stabilized by hydrophobic interactions, the peptides corresponding to turns in the folded protein do not measurably populate beta-turn conformations in water, and the addition of trifluoroethanol does not enhance the formation of either helical or turn structure. In contrast to the series of peptides described here, either studies of peptides from the GH region of myoglobin show a marked tendency to populate helical structures (H), nascent helical structures (G), or turn conformations (GH peptide) in water solution. This region, together with the A-helix and part of the B-helix, has been shown to participate in an early folding intermediate. The complete analysis of conformational properties of isolated myoglobin peptides supports the hypothesis that spontaneous secondary structure formation in local regions of the polypeptide may play an important role in the initiation of protein folding.

Amino Acid Sequence↗
PubMed1990

Crystal structure of myoglobin from a synthetic gene.

Crystals have been grown of myoglobin produced in Escherichia coli from a synthetic gene, and the structure has been solved to 1.9 A resolution. The space group of the crystals is P6, which is different from previously solved myoglobin crystal forms. The synthetic myoglobin is essentially identical to myoglobin isolated from sperm whale tissue, except for the retention of the initiator methionine at the N-terminus and the substitution of asparagine for aspartic acid at position 122. Superposition of the coordinates of native and synthetic sperm whale myoglobins reveals only minor changes in the positions of main chain atoms and reorientation of some surface side chains. Crystals of variants of the "synthetic" myoglobin have also been grown for structural analysis of the role of key amino acid residues in ligand binding and specificity.

Escherichia coli↗
PubMed1992

The correct molecular weight of myoglobin, a common calibrant for mass spectrometry.

Myoglobins from horse heart muscle, horse skeletal muscle and sperm whale are widely used as calibration standards or test compounds for various mass spectrometric methodologies. In all such cases reported in the literature, a molecular weight value is used (16,950.5 and 17,199, respectively) which is based on the assumption that amino acid 122 in this 153 amino-acid-long protein is asparagine, overlooking a published suggestion that it is aspartic acid instead. Since the mass assignment accuracy for matrix-assisted laser desorption mass spectrometry is reported to be +/- 0.01% and for electrospray ionization +/- 0.0025%, and error of one mass unit in approximately 17,000 would be significant. The mass-to-charge ratio of ions of the tryptic peptide encompassing amino acid 122 derived from commercially available horse heart and horse skeletal myoglobins, the apomyoglobin of the latter, and the tryptic and chymotryptic peptide of sperm whale myoglobin proved that in both proteins amino acid 122 is indeed aspartic acid, rather than asparagine. This finding was further confirmed by the collision-induced dissociation spectra of the [M + H]+ ions of the tryptic peptides from the horse myoglobins and the chymotriptic peptide from sperm whale myoglobin. Thus, the correct molecular weight of horse myoglobin is 16,951.49 and that of the sperm whale protein is 17,199.91.

Amino Acid Sequence↗
PubMed1995

Structural and functional effects of apolar mutations of the distal valine in myoglobin.

High-resolution structures of the aquomet, deoxy, and CO forms of Ala68, Ile68, Leu68, and Phe68 sperm whale myoglobins have been determined by X-ray crystallography. These 12 new structures, plus those of wild-type myoglobin, have been used to interpret the effects of mutations at position 68 and the effects of cobalt substitution on the kinetics of O2, CO, and NO binding. Molecular dynamics simulations based on crystal structures have provided information about the time-dependent behavior of photolyzed ligands for comparison with picosecond geminate recombination studies. The Val68-->Ala mutation has little effect on the structure and function of myoglobin. In Ala68 deoxymyoglobin, as in the wild-type protein, a water molecule hydrogen-bonded to the N epsilon atom of the distal histidine restricts ligand binding and appears to be more important in regulating the function of myoglobin than direct steric interactions between the ligand and the C gamma atoms of the native valine side-chain. This distal pocket water molecule is displaced by the larger side-chains at position 68 in the crystal structures of Leu68 and Ile68 deoxymyoglobins. The Leu68 side-chain can rotate about its C alpha-C beta and C beta-C gamma bonds to better accommodate bound ligands, resulting in net increases in overall association rate constants and affinities due to the absence of the distal pocket water molecule. However, the flexibility of Leu68 makes simulation of picosecond NO recombination difficult since multiple starting conformations are possible. In the case of Ile68, rotation of the substituted side-chain is restricted due to branching at the beta carbon, and as a result, the delta methyl group is located close to the iron atom in both the deoxy and liganded structures. The favorable effect of displacing the distal pocket water molecule is offset by direct steric hindrance between the bound ligand and the terminal carbon atom of the isoleucine side-chain, resulting in net decreases in affinity for all three ligands and inhibition of geminate recombination which is reproduced in the molecular dynamics simulations. In Phe68 myoglobin, the benzyl side-chain is pointed away from the ligand binding site, occupying a region in the back of the distal pocket. As in wild-type and Ala68 myoglobins, a well-defined water molecule is found hydrogen bonded to the distal histidine in Phe68 deoxymyoglobin. This water molecule, in combination with the large size of the benzyl side-chain, markedly reduces the speed and extent of ligand movement into the distal pocket. (ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Rapid, simple and sensitive microassay for skeletal and cardiac muscle myoglobin and hemoglobin: use in various animals indicates functional role of myohemoproteins.

A novel, simple, rapid, sensitive and reproducible microassay is described for determination of myoglobin and hemoglobin content of myocardial and skeletal muscle biopsy specimens from various mammals, birds and fish. As little as 50 mg of tissue is needed and myoglobin concentrations lower than 1 mg% can be detected. Myoglobin and hemoglobin are separated at alkaline pH by ammonium sulfate extraction followed by ultrafiltration. Heme content is determined by absorption of the Soret band when the hemoprotein extract is visibly colored or more sensitively by its peroxidase activity when the extract has low color. The heme reacts with tertiary-butyl hydroperoxide and orthotolidine to generate a blue color. Hemoglobin content is correlated with myoglobin content and is related to aerobic capacity and blood flow to the tissue. Myoglobin content varied over 5 orders of magnitude up to 7 per cent of the weight of tissue, whereas hemoglobin content varied over 2 orders of magnitude up to 6 per cent of tissue weight. Myoglobin content is increased in species with high basal metabolic rate, high physical activity, prolonged diving capacity, fatigue resistance, and red muscle, whereas it is decreased in white muscle, iron-deficient animals, animals with sedentary lifestyles, and in animals and tissues with small fiber diameters such as avian or fish hearts.

Animals↗
PubMed1985

Serum myoglobin concentrations are decreased by beta-adrenergic stimulation.

During infusion with adrenaline in healthy subjects there was a more than 50% reduction in serum myoglobin concentrations. This effect appeared to be specific for beta-adrenergic stimulation, since no changes were seen after prior IV beta-blockade with propranolol, nor did noradrenaline affect the serum myoglobin levels. Oral beta-blockade with propranolol raised the basal serum levels of myoglobin and enhanced the exercise-related rise in serum myoglobin concentrations during ergometer cycling to exhaustion. These observations thus indicate that the beta-adrenergic system affects serum myoglobin concentrations. This should be kept in mind in the evaluation of myoglobin measurements for clinical purposes, and might reflect a physiologically relevant mechanism.

Adrenergic beta-Antagonists↗
PubMed1983

Myoglobin concentration in single type I and type II muscle fibres in man.

Histochemical visualization of myoglobin in a benzidine peroxidase reaction suggests that human skeletal muscle fibres are differentiated into fibres having either high or a low myoglobin content. In the present study myoglobin was quantified in single human muscle fibres after being classified as either type I ("slow-twitch") or type II ("fast twitch"). Samples were obtained from m. quadriceps femoris in 4 healthy untrained male subjects using the needle biopsy technique. After freeze-drying, individual fibres were dissected out and classified as either type I or type II by a myofibrillar ATPase stain. Myoglobin analyses were performed on these single fibres by a radioimmunoassay. The myoglobin concentrations were found to be significantly higher in type I than in type II muscle fibres in all 4 subjects and were, on the average, of the same magnitude as found in larger (mixed muscle) samples. The myoglobin concentration ratio between type I and type II fibres ranged from 1.4 to 1.7.

Humans↗
PubMed1989

Comparative oxygen affinity of fish and mammalian myoglobins.

Myoglobins from rat, coho salmon (Oncorhynchus kisutch), buffalo sculpin (Enophrys bison) hearts, and yellowfin tuna (Thunnus albacares) red skeletal muscle were partially purified and their O2 binding affinities determined. Commercially prepared sperm whale myoglobin was employed as an internal standard. Tested at 20 degrees C, myoglobins from salmon and sculpin bound O2 with lower affinity than myoglobins from the rat or sperm whale. Oxygen binding studies at 12 degrees C and 37 degrees C suggest that this difference is adaptive, permitting myoglobins from cold-adapted fish to function at physiologically relevant temperatures. Taken together, purification and O2 binding data obtained in this study reveal a previously unrecognized diversity of myoglobin structure and function.

Animals↗
PubMed1992

Effects of amino acid substitutions outside an antigenic site on protein binding to monoclonal antibodies of predetermined specificity obtained by peptide immunization: demonstration with region 15-22 (antigenic site 1) of myoglobin.

Monoclonal antibodies (mAbs) of predetermined specificity were prepared by immunizing with a free (i.e., not conjugated to any carrier) synthetic peptide representing region 15-22 (site 1) of sperm whale myoglobin (SpMb). The cross-reactions of Mb variants with three mAbs were studied in order to determine whether such interactions are influenced by substitutions outside the site. Finback whale Mb, which has no substitutions within region 15-22, showed lower cross-reactivity and relative binding affinity than the reference antigen, SpMb. Bottle-nose Atlantic dolphin myoglobin (BdMb) and badger myoglobin (BgMb), although they have identical substitutions within region 15-22 (Ala-15 to Gly and Val-21 to Leu), showed very different binding properties. The cross-reaction of BdMb was quite comparable to that of SpMb, while that of BgMb was much lower. Since the two proteins have identical structures in regions 15-22, the differences in their cross-reactivities are readily attributed to the effects of substitutions outside this region. Another pair of myoglobins, horse myoglobins (HsMb) and chicken myoglobin (ChMb), also have two identical substitutions (Ala-15 to Gly and Val-21 to Ile) within region 15-22, but possessed different cross-reactivity. The results indicate that the reaction of mAbs, whose specificity is precisely known and predetermined by the immunizing free peptide, can be markedly affected by substitutions outside the indicated binding region on the protein.

Amino Acid Sequence↗
PubMed1990

[Effect of heat on the solubility and the electrophoretic behavior of myoglobin].

The heat stability of beef myoglobin was investigated by means of its solubility and intensity of protein bands separated by isoelectric focusing. A method for the sensitive determination of myoglobin in the extracts was developed based on its ability to form a red dye by the oxidative coupling of 2,4-dichlorophenol and 4-aminoantipyrine in the presence of hydrogen peroxide. By this method, myoglobin could be determined to a concentration of 0.01 mg/ml. For the detection of electro-focused myoglobins, o-dianisidine has proved to be the most sensitive compound. The myoglobin content of the extracts, according to the intensity of the myoglobin bands in the electrophoretic gel, decreased with increasing temperature and heating-time. However, the position of the bands was not changed by the heat treatment.

Animals↗
PubMed1998

The cDNA-derived amino acid sequence of indoleamine dioxygenase like-myoglobin from the gastropod mollusc Omphalius pfeifferi.

Myoglobin was isolated from the radular muscle of the archaegastropod mollusc Omphalius pfeifferi (Trochidae). The molecular mass was estimated by SDS-PAGE to be about 40 kDa, 2.5 times larger than that of usual myoglobin. The cDNA for Omphalius myoglobin was amplified by polymerase chain reaction, and the cDNA-derived amino acid sequence of 375 residues was determined, of which 73 residues were identified directly by the chemical sequencing of internal peptides. The amino acid sequence of Omphalius myoglobin showed no significant homology with any other usual 16-kDa globins, but showed 84% and 36% identities with indoleamine dioxygenase-like myoglobins from Battilus (Turbinidae) and Sulculus (Haliotiidae), respectively. It also shows significant homology (26% identity) with human indoleamine 2,3-dioxygenase, a tryptophan-degrading enzyme containing heme. The distribution of indoleamine dioxygenase-like myoglobins suggests that they must have arisen exclusively along the specified lineage including the three families Haliotiidae, Turbinidae, and Trochidae of Archaegastropoda in molluscan evolution.

Amino Acid Sequence↗
PubMed2004

Carbohydrate supplementation and alterations in neutrophils, and plasma cortisol and myoglobin concentration after intense exercise.

The present study examined the effect of carbohydrate supplementation on changes in neutrophil counts, and the plasma concentrations of cortisol and myoglobin after intense exercise. Eight well-trained male runners ran on a treadmill for 1 h at 85% maximal oxygen uptake on two separate occasions. In a double-blind cross-over design, subjects consumed either 750 ml of a 10% carbohydrate (CHO) drink or a placebo drink on each occasion. The order of the trials was counter-balanced. Blood was drawn immediately before and after exercise, and 1 h after exercise. Immediately after exercise, neutrophil counts (CHO, 49%; placebo, 65%; P<0.05), plasma concentrations of glucose (CHO, 43%; P<0.05), lactate (CHO, 130%; placebo, 130%; P<0.01), cortisol (CHO, 100%; placebo, 161%; P<0.01), myoglobin (CHO, 194%; placebo, 342%; P<0.01) all increased significantly. One hour post-exercise, plasma myoglobin concentration (CHO, 331%; placebo, 482%; P<0.01) and neutrophil count (CHO, 151%; placebo, 230% P<0.01) both increased further above baseline. CHO significantly attenuated plasma myoglobin concentration and the neutrophil count after exercise (P<0.01), but did not affect plasma cortisol concentration. The effects of CHO on plasma myoglobin concentration may be due to alterations in cytokine synthesis, insulin responses or myoglobin clearance rates from the bloodstream during exercise. Plasma cortisol responses to CHO during exercise may depend on the intensity of exercise, or the amount of CHO consumed. Lastly, cortisol appears to play a minor role in the mobilisation of neutrophils after intense exercise.

Adult↗
PubMed1979

Influence of steric factors on oxygen binding. I. Studies on 2,4-diisopropyldeuteroheme-myoglobin.

Sperm whale apomyoglobin was recombined with 2,4-diisopropyldeuterohemin to form 2,4-diisopropyldeuteroheme-myoglobin and its various physico-chemical properties were investigated to get an insight into the structural and functional role of the peripheral vinyl groups. 2,4-Diisopropyldeuteroheme-myoglobin showed a four times lower oxygen affinity at 25 degrees C and larger enthalpy and entropy changes of oxygenation than the corresponding values of native myoglobin. 2,4-Diisopropyldeuteroheme-metmyoglobin shows a pKa value of 9.68 which is higher than those of native metmyoglobin and mesoheme-metmyoglobin. The rate of autooxidation of oxy-form was about seven times larger in 2,4-diisopropyldeuteroheme-myoglobin than in native myoglobin. The electron-donating effect of isopropyl groups does not give straightforward explanation for these anomalous properties of 2,4-diisopropyldeuteroheme-myoglobin. It is proposed that site and stereospecific van der Waals' interaction between the polypeptide side chains and the peripheral 2,4-diisopropyl groups may weaken the interaction between the bound oxygen molecule and the distal His, resulting in the decrease in the stability of oxyform.

Animals↗