Myoglobin

3RGK415117189ENSG00000198125ENSMUSG00000018893P02144P04247NM_005368NM_203377NM_203378NM_001362846NM_001164047NM_001164048NM_013593NP_005359NP_976311NP_976312NP_001349775NP_001157519NP_001157520NP_038621Myoglobin (symbol Mb or MB) is an iron- and oxygen-binding protein found in the muscle tissue of vertebrates in general and in almost all mammals. It is distantly related to hemoglobin which is the iron- and oxygen-binding protein in blood, specifically in the red blood cells. In humans, myoglobin is only found in the bloodstream after muscle injury. It is an abnormal finding, and can be diagnostically relevant when found in blood.1m6c: V68N MYOGLOBIN WITH CO1m6m: V68N MET MYOGLOBIN1mdn: WILD TYPE MYOGLOBIN WITH CO1mnh: INTERACTIONS AMONG RESIDUES CD3, E7, E10 AND E11 IN MYOGLOBINS: ATTEMPTS TO SIMULATE THE O2 AND CO BINDING PROPERTIES OF APLYSIA MYOGLOBIN1mni: ALTERATION OF AXIAL COORDINATION BY PROTEIN ENGINEERING IN MYOGLOBIN. BIS-IMIDAZOLE LIGATION IN THE HIS64-->VAL(SLASH)VAL68-->HIS DOUBLE MUTANT1mnj: INTERACTIONS AMONG RESIDUES CD3, E7, E10 AND E11 IN MYOGLOBINS: ATTEMPTS TO SIMULATE THE O2 AND CO BINDING PROPERTIES OF APLYSIA MYOGLOBIN1mnk: INTERACTIONS AMONG RESIDUES CD3, E7, E10 AND E11 IN MYOGLOBINS: ATTEMPTS TO SIMULATE THE O2 AND CO BINDING PROPERTIES OF APLYSIA MYOGLOBIN1mno: V68N MYOGLOBIN OXY FORM1mwc: WILD TYPE MYOGLOBIN WITH CO1mwd: WILD TYPE DEOXY MYOGLOBIN1myg: HIGH RESOLUTION X-RAY STRUCTURES OF PIG METMYOGLOBIN AND TWO CD3 MUTANTS MB(LYS45-> ARG) AND MB(LYS45-> SER)1myh: HIGH RESOLUTION X-RAY STRUCTURES OF PIG METMYOGLOBIN AND TWO CD3 MUTANTS MB(LYS45-> ARG) AND MB(LYS45-> SER)1myi: HIGH RESOLUTION X-RAY STRUCTURES OF PIG METMYOGLOBIN AND TWO CD3 MUTANTS MB(LYS45-> ARG) AND MB(LYS45-> SER)1myj: DISTAL POLARITY IN LIGAND BINDING TO MYOGLOBIN: STRUCTURAL AND FUNCTIONAL CHARACTERIZATION OF A THREONINE68(E11) MUTANT1pmb: THE DETERMINATION OF THE CRYSTAL STRUCTURE OF RECOMBINANT PIG MYOGLOBIN BY MOLECULAR REPLACEMENT AND ITS REFINEMENT1yca: DISTAL POCKET POLARITY IN LIGAND BINDING TO MYOGLOBIN: DEOXY AND CARBONMONOXY FORMS OF A THREONINE68 (E11) MUTANT INVESTIGATED BY X-RAY CRYSTALLOGRAPHY AND INFRARED SPECTROSCOPY1ycb: DISTAL POCKET POLARITY IN LIGAND BINDING TO MYOGLOBIN: DEOXY AND CARBONMONOXY FORMS OF A THREONINE68 (E11) MUTANT INVESTIGATED BY X-RAY CRYSTALLOGRAPHY AND INFRARED SPECTROSCOPY2mm1: X-RAY CRYSTAL STRUCTURE OF A RECOMBINANT HUMAN MYOGLOBIN MUTANT AT 2.8 ANGSTROMS RESOLUTION Myoglobin (symbol Mb or MB) is an iron- and oxygen-binding protein found in the muscle tissue of vertebrates in general and in almost all mammals. It is distantly related to hemoglobin which is the iron- and oxygen-binding protein in blood, specifically in the red blood cells. In humans, myoglobin is only found in the bloodstream after muscle injury. It is an abnormal finding, and can be diagnostically relevant when found in blood. Myoglobin is the primary oxygen-carrying pigment of muscle tissues. High concentrations of myoglobin in muscle cells allow organisms to hold their breath for a longer period of time. Diving mammals such as whales and seals have muscles with particularly high abundance of myoglobin. Myoglobin is found in Type I muscle, Type II A and Type II B, but most texts consider myoglobin not to be found in smooth muscle. Myoglobin was the first protein to have its three-dimensional structure revealed by X-ray crystallography. This achievement was reported in 1958 by John Kendrew and associates. For this discovery, John Kendrew shared the 1962 Nobel Prize in chemistry with Max Perutz. Despite being one of the most studied proteins in biology, its physiological function is not yet conclusively established: mice genetically engineered to lack myoglobin can be viable and fertile but show many cellular and physiological adaptations to overcome the loss. Through observing these changes in myoglobin-deplete mice, it is hypothesised that myoglobin function relates to increased oxygen transport to muscle, oxygen storage and as a scavenger of reactive oxygen species. In humans myoglobin is encoded by the MB gene. Myoglobin can take the forms oxymyoglobin (MbO2), carboxymyoglobin (MbCO), and metmyoglobin (met-Mb), analogously to hemoglobin taking the forms oxyhemoglobin (HbO2), carboxyhemoglobin (HbCO), and methemoglobin (met-Hb). Like hemoglobin, myoglobin is a cytoplasmic protein that binds oxygen on a heme group. It harbors only one heme group, whereas hemoglobin has four. Although its heme group is identical to those in Hb, Mb has a higher affinity for oxygen than does hemoglobin. This difference is related to its different role: whereas hemoglobin transports oxygen, myoglobin's function is to store oxygen. Myoglobin contains hemes, pigments responsible for the colour of red meat. The colour that meat takes is partly determined by the degree of oxidation of the myoglobin. In fresh meat the iron atom is in the ferrous (+2) oxidation state bound to an oxygen molecule (O2). Meat cooked well done is brown because the iron atom is now in the ferric (+3) oxidation state, having lost an electron. If meat has been exposed to nitrites, it will remain pink because the iron atom is bound to NO, nitric oxide (true of, e.g., corned beef or cured hams). Grilled meats can also take on a pink 'smoke ring' that comes from the iron binding to a molecule of carbon monoxide. Raw meat packed in a carbon monoxide atmosphere also shows this same pink 'smoke ring' due to the same principles. Notably, the surface of this raw meat also displays the pink color, which is usually associated in consumers' minds with fresh meat. This artificially induced pink color can persist, reportedly up to one year. Hormel and Cargill are both reported to use this meat-packing process, and meat treated this way has been in the consumer market since 2003. Myoglobin is released from damaged muscle tissue (rhabdomyolysis), which has very high concentrations of myoglobin. The released myoglobin is filtered by the kidneys but is toxic to the renal tubular epithelium and so may cause acute kidney injury. It is not the myoglobin itself that is toxic (it is a protoxin) but the ferrihemate portion that is dissociated from myoglobin in acidic environments (e.g., acidic urine, lysosomes). Myoglobin is a sensitive marker for muscle injury, making it a potential marker for heart attack in patients with chest pain. However, elevated myoglobin has low specificity for acute myocardial infarction (AMI) and thus CK-MB, cardiac Troponin, ECG, and clinical signs should be taken into account to make the diagnosis.