Showing papers on "Myoglobin published in 1984"

Cavities in proteins: structure of a metmyoglobin-xenon complex solved to 1.9 A.

Abstract: X-ray crystallographic data to 1.9-A resolution were collected on sperm whale metmyoglobin equilibrated with 7 atm of xenon gas. The results indicate four xenon sites of occupancy from 0.45 to 1.0. These sites are located in interior spaces or packing defects of the myoglobin molecule. The effects of the bound xenon on the protein structure are minor, and we observe a small overall reduction in refined isotropic atomic protein temperature factors. We interpret the results as a confirmation that, on a time-averaged basis, cavities exist within the myoglobin molecule and suggest that the binding of small ligands in these cavities affects the internal motions and conformational substrates of the protein.

Reaction of myoglobin with phenylhydrazine: a molecular doorstop.

Abstract: X-ray crystallographic studies of myoglobin do not show an entrance or exit path for potential ligands from the surface to the heme cavity. Efforts to locate such a path have so far centered around dynamic calculations. A structure has now been determined that has a clear opening. Phenylhydrazine reacts with myoglobin in such a way that a phenyl group remains bound to the iron atom. The structure of this complex shows that the side chains of His-64(E7), Arg-45-(CD3), and Val-68(E11) have been forced aside to form an open channel to the surface. Although this may not be the only channel to the iron atom, it seems likely that it is an important one.

A consistent picture of protein dynamics.

Abstract: Information about the protein dynamics of myoglobin obtained by x-ray and Mossbauer investigations is analyzed and compared with computer simulations. Computer simulations give correct amplitudes of mean-square displacements but fail in the description of the time dependence of motions. Our model describes protein dynamics at physiological temperatures as an overdamped diffusion-like motion in a restricted space. The fluctuations occur around the average conformation determined by x-ray structure analysis. The gain in entropy drives the molecule into the transition state and, in this way, accounts for its flexibility.

Myoglobin levels in individual human skeletal muscle fibers of different types.

Abstract: An attempt was made to determine the relationship of myoglobin content to specific fiber types in human muscle. Biopsies were obtained from biceps brachii, vastus lateralis, and gastrocnemius muscles of untrained subjects and from the vastus lateralis muscle of a highly trained athlete at peak training and at intervals of no training (detraining). Individual muscle fibers were assayed, by quantitative microanalytical methods, for myoglobin, lactate dehydrogenase, malate dehydrogenase, citrate synthase, beta-hydroxyacyl-coenzyme A dehydrogenase, and adenylokinase activities all on the same fiber. The enzyme levels were used to classify the fibers into type I or II. The results show that the content of myoglobin in human muscle does not differ greatly between fiber types in contrast to other species. The type II fibers contained, on the average, at least two-thirds as much myoglobin as type I fibers. The concentration of myoglobin did not change in either fiber type during detraining (84 days), despite marked changes in lactate dehydrogenase, adenylokinase and the three oxidative enzymes.

T cell recognition of myoglobin. Localization of the sites stimulating T cell proliferative responses by synthetic overlapping peptides encompassing the entire molecule.

Abstract: SUMMARY A comprehensive strategy for the systematic localization of all continuous antigenic sites within a protein has previously been introduced by this laboratory. The strategy consists of studying the immunochemical activity of a series of consecutive synthetic peptides that encompass the entire protein chain and the are uniform in size and in overlap at their N and C-terminals with neighbouring peptided. By application of this strategy to sperm whale myoglobin, we have been able to delineate the ontinuous sites of T cell recognition of myoglobin in three high responder mouse strains. Thirteen 17-residue peptides that encompass the entire myoglobin chain and overlap by five residues at both ends were synthesized, purified and characterized. The peptides were examined in vitro for their ability to stimulate lymph node cells from myoglobin-primed DBA/2 (H-2d), BALB/c (H-2d) and SJL (H-2s) mice as well as long-term cultures of myoglobin-specific T cells. Several regions of the moleculr (T sites) were founnd to stimulate myoglobin-primed lymph node cells and myoglobin-specific long-term T cell cultures. This strategy has enabled the localization of the full profile of dominant sites of T cell recognition in myoglobin for these mouse strains. Of these T sites, one region, residues 107-125, was clearly immunodominant in these strains and was found to coincide with the antigenic (i.e. antibody binding) site 4 of myoglobin. Also, other regions stimulated T cells and appeared to coincide with previously known antigenic sites. It is noteworthy that, in addition to sites recognized by both T and B cells, the protein has other sites which are recognized exclusively by T cells and to which no detectable antibody response is directed.

Myoglobin and creatine kinase in acute myocardial infarction.

Abstract: Serum myoglobin concentration and creatine kinase activity were measured serially in 70 consecutive patients presenting within four hours of the onset of symptoms of suspected acute myocardial infarction. Of 36 patients with definite or possible myocardial infarction (WHO criteria), the serum myoglobin concentration was raised (greater than 85 micrograms/l) one hour after the onset of symptoms in 25% and at four hours in 89%. Creatine kinase activity was raised (greater than 140 U/l) one hour after the onset in 25% and at four hours in only 56%. Within 12 hours of the onset of symptoms the myoglobin concentration reached a peak in 83% and the creatine kinase a peak in only 14%. Within 36 hours the myoglobin concentration fell to normal values in 67% while creatine kinase activity fell to normal values in only 3%. Four hours after the onset of symptoms the serum myoglobin concentration distinguished easily those patients with myocardial infarction from those without, whereas when creatine kinase values were used the sensitivity was poor but the specificity high. From the combined results of the two studies and using a single measurement of serum myoglobin concentration at six hours from the onset of symptoms to predict the diagnosis in 114 patients with suspected infarction, the sensitivity was 93% and specificity 89%.

Detection of hypothyroid myopathy by measurement of various serum muscle markers-myoglobin, creatine kinase, lactate dehydrogenase and their isoenzymes: correlations with thyroid hormone levels (free and total) and clinical usefulness

Abstract: An accurate and close follow-up of serum levels of thyroid hormones and various muscle markers (myoglobin, creatine kinase and its isoenzymes CK-MB and CK-BB, lactic dehydrogenase, α-hydroxybutyric de

Myoglobin content in human skeletal muscle and myocardium: relation to fibre size and oxidative capacity.

Abstract: Myoglobin, muscle fibre diameter, and citrate synthase activity were measured in leg muscle of untrained and trained men and in the myocardium from the apex of the left ventricle and from papillary muscle in patients subjected to open heart surgery. The citrate synthase (CS) activity was 60% higher in trained than in untrained skeletal muscle. In the myocardium it was around four times greater than in untrained skeletal muscle but there was no difference between the apex of the left ventricle and papillary muscle. The fibre diameter varied almost threefold between the different groups of muscles with the largest diameter in untrained skeletal muscle and the with the largest diameter in untrained skeletal muscle and the smallest in papillary muscle. The myoglobin content in trained skeletal muscle did not differ from that of untrained muscle. In the left ventricle it was only 40% of that found in untrained muscle while papillary muscle had almost twice as high a myoglobin content as did the left ventricle. The ratio between myoglobin and fibre diameter, however, was of similar magnitude in skeletal muscle and the left ventricle while it was twice as high in papillary muscle as in the other muscles. In conclusion, the diffusion distance in terms of fibre diameter decreased with increased oxidative capacity (CS activity), when comparing the statistical means of the four different groups. The capacity for oxygen diffusion in relation to oxygen demand measured as the ratio of myoglobin to fibre diameter appeared to be of similar magnitude in skeletal muscle and left ventricle but was higher in papillary muscle.

The activity of tissue enzymes in iron-deficient rat and man: an overview.

Abstract: 1. 1. The effects of iron deficiency in rat and/or man on iron-containing enzymes of different tissues is reviewed. 2. 2. Iron deficiency results in a decrease of skeletal muscle iron containing proteins e.g. myoglobin, cytochromes c, a − a 3 , and α-glycerophosphate oxidase. 3. 3. Iron deficiency produces a reduction in the activity of several respiratory enzymes in the mitochondrial fraction of cardiac muscle, particularly: NADH cytochrome c reductase, succinic cytochrome c reductase, succinic dehydrogenase and NADH ferricyanide oxidoreductase. 4. 4. The effects of iron deficiency on brain tissue is emphasized with respect to cytochromes, monoaminoxidase and amino acids metabolism. 5. 5. Host defence to infection (controversial data), decrease in body temperature, alteration of DNA synthesis, collagen and lipid metabolism, liver and gastrointestinal mucous cytochromes activity perturbations are discussed.

The Influence of Age and Endurance Exercise on the Myoglobin Concentration of Skeletal Muscle of the Rat

Abstract: The myoglobin concentrations of gastrocnemius muscles of 2-, 5-, 9-, and 25-month-old sedentary, 25-month-old weight-restricted, and 25-month-old endurance-trained (treadmill running) Sprague-Dawley male rats were determined. The concentration of myoglobin was greater in the 5-month-old than in the 2-month-old rat and was lower in the 9- than in the 5-month-old rat. The gastrocnemius myoglobin concentration was the same for 9- and 25-month-old animals. Four months of endurance training, starting at 21 months of age, resulted in gastrocnemius myoglobin concentrations greater than either that of the 25-month-old weight-matched, calorie-restricted control or the 25-month-old sedentary control groups. The gastrocnemius myoglobin concentration of the elderly trained group was intermediate between that of the 5- and 9-month-old animals. These results are consistent with the known loss of oxidative capacity of skeletal muscle with age and its restoration with endurance exercise.

Comparison of the magnetic properties of deoxy- and photodissociated myoglobin

Abstract: The magnetic susceptibility of photodissociated carbon monoxy myoglobin has been measured over the temperature range from 1.7 to 25 K at 10 and 50 kG with a superconducting susceptometer. The spin and the crystal field parameters of the iron ion were extracted by a spin Hamiltonian approach. Under equivalent conditions the magnetic susceptibility of deoxy myoglobin was measured. In both experiments the CO-bound protein was used as a diamagnetic reference. Above about 5 K the metastable photolysed state and the equilibrium deoxy form of myoglobin are magnetically indistinguishable and can be fitted with S = 2 and g = 2. The transition from spin 0 to spin 2 and the conformational changes known to accompany the electronic change thus also occur after photolysis at low temperature. At temperatures below 5 K, differences become apparent, indicating a somewhat smaller zero-field splitting in the photoproduct as compared to the ligand-free state at equilibrium. In qualitative agreement with observations made by other techniques, the data imply that even at 1.7 K substantial structural relaxation occurs in the heme region of myoglobin after photodissociation. The results are important for the interpretation of the ligand binding kinetics after flash photolysis at low temperature and contribute to the understanding of the relationship between electronic structure and function in heme proteins.

Modification of the heme distal side in myoglobin by cyanogen bromide. Heme environmental structures and ligand binding properties of the modified myoglobin

Abstract: Met, deoxy, and CO forms of myoglobin (Mb) react with a stoichiometric amount of cyanogen bromide (BrCN) to cause substantial changes in the 1H NMR, optical absorption, and infrared spectra. These spectral changes were interpreted as arising from the substantial alterations in the heme environments, most probably due to the modification of the histidine residue at the heme distal side. It is also revealed that the modified Mb does not combine with some exogenous ligands such as CN-, CH3NH2, and O2, although it does with N-3 or CO. These unique ligand binding properties are also discussed with relevance to a role of the distal histidine in stabilizing the coordinated ligand through a hydrogen bond and to a steric constraint.

The physiological role of myoglobin: more than a problem in reaction-diffusion kinetics

Abstract: Oxygen has a very low solubility in aqueous solutions, and with rare exceptions we find that oxygen is carried in the circulation almost entirely in combination with a special oxygen-binding protein. Four main types of such proteins are found in the animal kingdom: hemoglobins, chlorocruorins, hemerythrins, and hemocyanins. The most widely distributed in the animal kingdom are the hemoglobins, which are found in all phyla. The chlorocruorins are modified hemoglobins found in only a few families of polychaete worms. In evolutionary terms the hemoglobins are ancient molecules, and they come in many sizes. The large hemoglobins, of molecular weight around 106, are found only in invertebrates, Generally the large molecules are found free in the plasma, whereas the small ones are packaged in cells, the red blood cells. In red cells of almost all vertebrates hemoglobin is a tetramer of two similar basic chains; for example, in adult humans the tetramer consists of two a and two /3 chains. The monomers are of molecular weight (16-17)x 103. However, another molecule, a monomeric oxygen-binding globin called tissue hemoglobin or myoglobin, is found in heart and red skeletal muscle cells. It is found in invertebrates as well as vertebrates. This review is concerned with the function of myoglobin, but brings in hemoglobin because both have been used in some of the work on facilitated diffusion of oxygen. Myoglobin has been thought to serve as a long term and short term oxygen store [l]. In the muscles of diving mammals and birds the concentration of myoglobin is very high, giving the muscles a dark red to near-black color depending on the degree of oxygenation. In the divers it may serve as an oxygen store sufficient for a few minutes. In nondiving animals red muscles have much lower concentrations of myoglobin, and it has been suggested that the myoglobin serves as a short term store to provide oxygen

Identification of the titrating group in the heme cavity of myoglobin. Evidence for the heme-protein pi-pi interaction.

Abstract: The pH dependence of the proton NMR chemical shifts of met-cyano and deoxy forms of native and reconstituted myoglobins reflects a structural transition in the heme pocket modulated by a single proton with pK 5.1–5.6. Comparison of this pH dependence of sperm whale and elephant myoglobin and that of the former protein reconstituted with esterified hemin eliminates both the distal histidine as well as the heme propionates as the titrating residue. Reconstitution of sperm whale met-cyano myoglobin with hemin modified at the 2,4-positions leads to a systematic variation in the pK for the structural transition, thus indicating the presence of a coupling between the titrating group and the heme π system. The results are consistent with histidine FG3 (His-FG3) being the titrating group, and a donor-acceptor π-π interaction between its imidazole and the heme is proposed.

Myoglobin concentration, creatine kinase activity, and creatine kinase B subunit concentrations in serum during thyroid disease.

Abstract: Changes in values for myoglobin, total creatine kinase (EC 2.7.3.2), and creatine kinase B-subunit in the serum of patients with thyroid disease are compared with values for these during the 24-h after myocardial infarction. Concentrations of all three of these muscle-derived proteins were significantly higher than normal in patients with primary hypothyroidism, and declined with treatment. Values for total creatine kinase activity were below-normal in hyperthyroid patients, but increased after treatment. Values for total creatine kinase and, to a lesser extent, myoglobin in hypothyroidism extend into the range of values observed after myocardial infarction. The mechanism of the changes in these analytes in hypothyroidism may be related to increased leakage from skeletal-muscle cells or diminished clearance from the circulation, or both.

Ultrasonic absorption by solvent–solute interactions and proton transfer in aqueous solutions of peptides and small proteins

Abstract: Ultrasonic absorption values in aqueous solutions of myoglobin, apomyoglobin, α‐lactalbumin, bacitracin, and the C‐ and N‐terminal CNBr cleavage fragments of myoglobin were determined by the cylindrical resonator technique at temperatures of 4 °C and 20 °C in the frequency range 0.5–7 MHz. A proposed mechanism of absorption in solutions of proteins and peptides is perturbation by the ultrasound of the equilibrium between protein bound and free water, producing a distribution of relaxation processes occurring within the frequency range of the investigation. The hypothesis is supported by the dependence of the ultrasonic absorption on solute surface area and molecular weight. Another mechanism of absorption is that due to proton transfer which occurs noticeably in the presence of phosphate ions. Those proteins (myoglobin and α‐lactalbumin) with significant globular structure appear to undergo additional relaxation processes at frequencies above 7 MHz.