Myoglobin

• OMIM: 160000
• UniProt: P02144
• MGI: 96922

Myoglobin is a muscle protein (from Greek μυς, mys, muscle ' and Latin globus, ball ') from the group of globins, globular proteins that contain an oxygen-binding heme group. Myoglobin can absorb oxygen and release and is responsible for the intramuscular oxygen transport. It takes care of the oxygen in the blood from the hemoglobin, and outputs it at the site of physiological Combustion processes in the muscle cells again.

Scientific description

Myoglobin is a heme -based, globular, single chain protein of 153 amino acids with a molecular mass of 17,053 daltons (17 kDa), having the ability to transport oxygen (O2) reversibly binding. The secondary structure of the protein is composed of a total of eight α helices.

Under physiological conditions, it is present as a monomer. The active site of myoglobin is a heme b, ie a protoporphyrin IX with an excess of the four nitrogens of the ligated iron ( II) ion. Heme is bound via an axially coordinated to the central iron ion proximal histidine of the protein matrix. The second axial position is used for binding of the oxygen molecule.

In contrast to the structurally related hemoglobin myoglobin binds oxygen cooperatively not positive, but regardless of the oxygen concentration of the environment.

The presence of myoglobin is restricted to cardiac and skeletal muscle cells of mammals. Here it is in high concentrations (up to about 100 mol / l), giving the muscle tissue its red color. The oxygen uptake can be followed well absorption spectroscopy, the characteristic Soret band of the heme shifts markedly with oxygen intake of 418 to 434 nm

Myoglobin is one of the globins. The myoglobin closely related is the Cytoglobin described only in 2002, which is found in almost all cells of vertebrates. It presumably serves well as an oxygen reservoir in the cell. It even seems that myoglobin is well become during evolution by gene duplication which a muscle-specific variant of the Cytoglobins.

Importance

As the biological function of the oxygen transport in the cell of the cell membrane to the mitochondria considered. For this reason, its affinity for oxygen is also higher than that of hemoglobin, this promotes the transport of oxygen towards the cell interior. The observed when hemoglobin oxygen affinity regulation of missing the myoglobin. At least with marine mammals and the oxygen storage is being debated: Whales have a 5-10 times higher myoglobin content in their muscles than land mammals.

The myoglobin of the sperm whale, therefore, was the first protein to the John Kendrew 1958 structure determination ( X-ray) succeeded. This pioneering work was the basis for the subsequent elucidation of the structure of hemoglobin by Max Perutz (1959). Both scientists were awarded the 1962 Nobel Prize in Chemistry.

Importance in medicine

An increase in myoglobin concentration in blood serum of mammals can be considered as an indicator of a heart attack due to rhabdomyolysis. However, since an increased Myoglobinwert is non-specific, are used today for the creatine kinase cardiac diagnosis. Furthermore, increased Myoglobinwerte show in damage to the skeletal muscle (extreme sports, seizures, trauma, intramuscular injections, alcohol intoxication, muscle diseases, spills ( such as earthquakes ) ); these can at extremely elevated levels lead to acute renal failure (crush kidney).

The plasma half-life of myoglobin is only 10 to 20 minutes, since it is rapidly excreted via the kidney (glomerular filtration). The Myoglobinwert rises during a heart attack after approx 1-2 hours, and reaches its maximum after 4-6 hours. Already within 12-24 hours it drops back into the normal range.

Standard levels in humans in the blood: women and 35 g / l, men to 55 ug / l

Normal value in humans in urine: Women and men up to 0.3 mg / l