Myoglobin

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Myoglobin
Model of helical domains in myoglobin.
Gene code:	HUGO code: MB<ref>Symbol Report: MB. Retrieved on 2006-05-20.</ref>
Structure:	molecular structure<ref>Takano, T. "Structure of myoglobin refined at 2-0 A resolution. II. Structure of deoxymyoglobin from sperm whale". J. Mol. Biol. 110: 569-584.</ref>
Recent publications:	role in human pathologies,<ref>Reeder, BJ, Svistunenko DA, Cooper CE, Wilson MT (Dec 2004). "The radical and redox chemistry of myoglobin and hemoglobin: from in vitro studies to human pathology". Antioxid Redox Signal 6 (6): 954-66. PMID 15548893.</ref> gene knockout<ref>Schlieper, G, Kim JH, Molojavyi A, Jacoby C, Laussmann T, Flogel U, Godecke A, Schrader J (Apr 2004). "Adaptation of the myoglobin knockout mouse to hypoxic stress". Am J Physiol Regul Integr Comp Physiol 286 (4): R786-92. PMID 14656764.</ref>

<tr><td bgcolor=#e7dcc3 width=85>protein type:</td>

   <td style="border-top:1px solid #e7dcc3" width=220>Hemoprotein</td></tr>

<tr><td bgcolor=#e7dcc3 width=85>Functions:</td>

   <td style="border-top:1px solid #e7dcc3" width=220>oxygen storage/transport</td></tr>

<tr><td bgcolor=#e7dcc3 width=85>Domains:</td>

   <td style="border-top:1px solid #e7dcc3" width=220>globin<ref>globin, with user query added. NCBI. Retrieved on 2006-05-20.</ref></td></tr>

<tr><td bgcolor=#e7dcc3 width=85>Diseases:</td>

   <td style="border-top:1px solid #e7dcc3" width=220>kidney disease, vasospasm</td></tr>

<tr><td bgcolor=#e7dcc3 width=85>Taxa expressing:</td>

   <td style="border-top:1px solid #e7dcc3" width=220>many metazoan phyla,
Arhaea?<ref>ST1818   hypothetical myoglobin [Sulfolobus tokodaii str. 7 GeneID: 1459874 Locus tag: ST1818]. NCBI (03-Dec-2005). Retrieved on 2006-05-20.</ref>
 protozoan/eubacterial?<ref>glbN Probable hemoglobin glbN [Mycobacterium tuberculosis H37Rv GeneID:  886402 Locus tag: Rv1542c]. NCBI (21-Mar-2006). Retrieved on 2006-05-20.</ref></td></tr>

<tr><td bgcolor=#e7dcc3 width=85>Cell types:</td>

   <td style="border-top:1px solid #e7dcc3" width=220>muscle cells</td></tr>

<tr><td bgcolor=#e7dcc3 width=85>Subcellular localization:</td>

   <td style="border-top:1px solid #e7dcc3" width=220>cytoplasm</td></tr>

<tr><td bgcolor=#e7dcc3 width=85>covalent modifications</td>

   <td style="border-top:1px solid #e7dcc3" width=220>glycation?<ref>Roy, A, Sen S, Chakraborti AS (Feb 2004). "In vitro nonenzymatic glycation enhances the role of myoglobin as a source of oxidative stress". Free Radic Res. 38 (2): 139-46. PMID 15104207.</ref>
phosphorylation in whales?<ref>Stewart, JM, Blakely JA, Karpowicz PA, Kalanxhi E, Thatcher BJ, Martin BM (Mar 2004). "Unusually weak oxygen binding, physical properties, partial sequence, autoxidation rate and a potential phosphorylation site of beluga whale (Delphinapterus leucas) myoglobin". Comp Biochem Physiol B Biochem Mol Biol 137 (3): 401-12. PMID 15050527.</ref></td></tr>

<tr><td bgcolor=#e7dcc3 width=85>Other names:</td>

   <td style="border-top:1px solid #e7dcc3" width=220>myoglobin-like proteins in microorganisms<ref>Wu, G, Wainwright LM, Poole RK (2003). "Microbial globins". Adv Microb Physiol 47: 255-310. PMID 14560666.</ref></td></tr>

<tr><td bgcolor=#e7dcc3 width=85>Molecular interactions</td>

   <td style="border-top:1px solid #e7dcc3" width=220>oxygen,
heme,
carbon monoxide,
nitric oxide</td></tr>

<tr><td bgcolor=#e7dcc3 width=85>related articles:</td>

   <td style="border-top:1px solid #e7dcc3" width=220>X-ray crystallography,
Secondary structure</td></tr>

</table>

$An X-ray diffraction image for the protein myoglobin.$

Myoglobin is a single-chain globular protein of 153 amino acids, containing a heme (iron-containing porphyrin) prosthetic group in the center around which the remaining apoprotein folds. With a molecular weight of 16,700 Daltons, it is the primary oxygen-carrying pigment of muscle tissues<ref name="review">George A. Ordway and Daniel J. Garry (2004). "Myoglobin: an essential hemoprotein in striated muscle". Journal of Experimental Biology 207: pages 3441–3446. DOI:10.1242/jeb.01172.</ref>. Unlike the blood-borne hemoglobin, to which it is structurally related<ref name="family">Harvey Lodish, Arnold Berk, Lawrence S. Zipursky, Paul Matsudaira, David Baltimore and James Darnell (2000). “Evolutionary tree showing the globin protein family members myoglobin and hemoglobin”, Molecular Cell Biology, Fourth Edition, W. H. FREEMAN. ISBN 0-7167-3136-3.</ref>, this protein does not exhibit cooperative binding of oxygen, since positive cooperativity is a property reserved for multimeric proteins. Instead, the binding of oxygen by myoglobin is unaffected by the oxygen pressure in the surrounding tissue. Myoglobin is often cited as having an "instant binding tenacity" to oxygen given its hyperbolic oxygen dissociation curve. In 1958, John Kendrew and associates successfully determined the structure of myoglobin by high-resolution X-ray crystallography.<ref name="architecture">JC Kendrew, G Bodo, HM Dintzis, RG Parrish, H Wyckoff, and DC Phillips (1958). "A Three-Dimensional Model of the Myoglobin Molecule Obtained by X-Ray Analysis". Nature 181 (4610): pages 662-666. DOI:10.1038/181662a0 PMID 13517261.</ref> For this discovery, John Kendrew shared the 1962 Nobel Prize in chemistry with Max Perutz<ref name="nobel">The Nobel Prize in Chemistry 1962</ref>.

[edit] Role in disease

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 renal failure.<ref name="renal">Toshio Naka, Daryl Jones, Ian Baldwin, Nigel Fealy, Samantha Bates, Hermann Goehl, Stanislao Morgera, Hans H. Neumayer and Rinaldo Bellomo (2005). "Myoglobin clearance by super high-flux hemofiltration in a case of severe rhabdomyolysis: a case report". Critical Care 9: pages R90–R95. DOI:10.1186/cc3034.</ref>.

Myoglobin is a sensitive marker for muscle injury, making it a potential marker for myocardial infarction in patients with chest pain<ref name="diagnosis">M. Weber, M. Rau, K. Madlener, A. Elsaesser, D. Bankovic, V. Mitrovic and C. Hamm (2005). "Diagnostic utility of new immunoassays for the cardiac markers cTnI, myoglobin and CK-MB mass". Clinical Biochemistry 38: pages 1027–1030. Entrez PubMed 16125162.</ref>. Its lack of specificity and the cost of the analysis has prevented its widespread use.