Myoglobin (Mb)

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Introduction

Myoglobin is an iron- and oxygen-binding protein, serving as a reserve oxygen supply and facilitating oxygen transport in muscles. Myoglobin is a part of the globin superfamily of proteins, consisting of eight alpha helices connected by loops, with a total content of 154 amino acids and a molecular weight of 17.7 kDa ^{1, 2, 4}. It is structurally similar to hemoglobin, which is the iron- and oxygen binding protein in blood. A porphyrin ring containing iron is at the center of myoglobin. A proximal histidine group is directly bound to the iron while a distal histidine group allows for interaction with the O₂ substrate, encouraging binding of O₂ and not carbon monoxide ^2,4. Once O₂ is bound to the myoglobin, a structural change occurs to the iron center as the iron is oxidized to an oxidation state of 3+. This stabilizes the bound oxygen by causing it to have a negative charge. The O₂ binding is reversible and will be released when the tissue shows oxygen needs. This is especially important in situations where the body is starved for oxygen, such as anaerobic exercise ².

Lee Biosolutions manufactures myoglobin from human hearts for use in research and medical diagnostics manufacturing.

Diagnostic Relevance

When myoglobin is found in the bloodstream, this is abnormal and can be diagnostically relevant ³. Myoglobin is a sensitive marker for muscle injury and can be used as a potential marker in the blood for detection of heart attacks. Myoglobin is released from damaged muscle tissue into the bloodstream and is filtered by the kidneys, potentially causing acute kidney injury.

Identification

1.Accession #: P02144

2.Gene:

Myoglobin gene [MB] located on chromosome 22q12.3

Gene ID: 4151

Properties

1.Structure: Myoglobin consists of eight alpha helices connected by loops. The protein contains a total of 154 amino acids. In position 65, there is an oxygen binding heme distal ligand. In position 94, there is an oxygen binding heme proximal ligand ^{1, 2, 4}.

2.Post-Translational Modification: Receives a modified phosphoserine in position 4 and a modified phosphothreonine residue in position 68.

3.Function: Maintains a reserve oxygen supply and facilitates oxygen transport in muscles ^{2, 4}.

4.Molecular Weight: 17,700

5.Stability: Stable as liquid at -20 °C. Recertification required three years after DOM.

References

1.Garry, D. J. and Memmen, P. P. A. (2007) Molecular insights into the functional role of myoglobin. Hypoxia and the Circulation, 181-193.

2.Ordway, G. A. and Garry, D. J. (2004) Myoglobin: an essential hemoprotein in striated muscle. Journal of Experimental Biology 207, 3441-3446.

3.Elmadbouh, I., Mahfouz, R., Bayomy, N., Faried, W., and Ghanayem, N. (2012) The value of human heart-type fatty acid binding protein in diagnosis of patients with acute chest pain. The Egyptian Heart Journal 64, 179-184.

4.Garry, D. J., Kanatous, S. B., and Mammen, P. P. A. (2003) Emerging Roles of Myoglobin in the Heart. Trends Cardiovasc Med 13, 111-116.