Results for myoglobin
On this page:
 
Dictionary:

myoglobin

  ('ə-glō'bĭn) pronunciation
n.

A single-chain, iron-containing protein found in muscle fibers, structurally similar to a single subunit of hemoglobin and having a higher affinity for oxygen than hemoglobin of the blood.


 
 
Food and Fitness: myoglobin

A red iron-containing protein present in muscle. It combines with oxygen to form oxymyoglobin which acts as a small oxygen store of about 10 millilitres per kilogram of muscle. This source of oxygen seems to be particularly important during intermittent bursts of activity. Oxygen is released during activity and the oxymyoglobin restored during recovery periods. Muscle rich in myoglobin is sometimes called red muscle. It has a preponderance of slow-twitch muscle fibres and is adapted to endurance activities.

 

An iron-containing pigment present in muscle. It combines with oxygen to form oxymyoglobin. This acts as a store of oxygen that can be used during strenuous exercise. Each myoglobin molecule consists of a single polypeptide chain with a haem group which has an affinity for oxygen stronger than that of haemoglobin.

 
('əglō'bĭn) , protein molecule isolated from the cells of vertebrate skeletal muscle that is both a structural and functional relative of hemoglobin, the oxygen-transport protein of the blood of higher animals. Myoglobin, which is composed of a single polypeptide chain of 153 amino acid residues, has the ability to store oxygen by binding it to an iron atom; iron is part of myoglobin's essential chemical composition. The complete amino acid sequence of myoglobin has been determined; it is a relatively small protein with a molecular weight of approximately 17,000 grams per mole. The distribution of myoglobin among the higher animals is a reflection of its physiological function. It is found abundantly in the tissues of diving mammals, e.g., the whale, the seal, and the dolphin. High concentrations of myoglobin in these animals presumably allows them to store sufficient oxygen to remain underwater for long periods. Myoglobin is found abundantly in man only in cardiac muscle, which, by virtue of its essential function, must possess the capacity for continued activity when environmental oxygen concentrations are low. Myoglobin has been investigated intensely and is the first protein molecule to have been completely described in terms of its three-dimensional geometry. This achievement won the British scientist John Kendrew a share in the 1962 Nobel Prize for Chemistry.


 

The oxygen-transporting pigment of muscle, a conjugated protein resembling a single subunit of hemoglobin, being composed of one globin polypeptide chain and one heme group.


 
Wikipedia: myoglobin
Myoglobin
Myoglobin.png
Model of helical domains in myoglobin.
Gene code: HGNC symbol: MB[1]
Structure: molecular structure[2]
Recent publications: role in human pathologies,[3]
gene knockout[4]
protein type: Hemoprotein
Functions: oxygen storage/transport{100 times more affinity towards oxygen}
Domains: globin[5]
Diseases: kidney disease, vasospasm
Taxa expressing: many metazoan phyla,
Archaea?[6]
protozoan/eubacterial?[7]
Cell types: muscle cells
Subcellular localization: cytoplasm
covalent modifications glycation?[8]
phosphorylation in whales?[9]
Other names: myoglobin-like proteins in microorganisms[10]
Molecular interactions oxygen,
heme,
carbon monoxide,
nitric oxide
related articles: X-ray crystallography,
Secondary structure


An X-ray diffraction image for the protein myoglobin.
Enlarge
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.[11] Unlike the blood-borne hemoglobin, to which it is structurally related,[12] 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. High concentrations of myoglobin in muscle cells allow organisms to hold their breaths longer. In 1958, John Kendrew and associates successfully determined the structure of myoglobin by high-resolution X-ray crystallography.[13] For this discovery, John Kendrew shared the 1962 Nobel Prize in chemistry with Max Perutz.[14]

Meat color

Myoglobin forms pigments responsible for making meat red. The color that meat takes is partly determined by the charge of the iron atom in myoglobin and the oxygen attached to it. In its raw state, the iron atom has a charge of +2 and is bound to O2, an oxygen molecule. Meat cooked well done is brown because the iron atom has a charge of +3, having lost an electron, and is now bound to a water molecule (H2O). Under some conditions, meat can also remain pink all through cooking, despite being heated to high temperatures. 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 a molecule of carbon monoxide.[15]

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.[16]

Myoglobin is a sensitive marker for muscle injury, making it a potential marker for heart attack in patients with chest pain.[17] Its lack of specificity and the cost of the analysis has prevented its widespread use.

Structure and bonding

Myoglobin consists of a porphyrin ring with an iron center. There is a proximal histidine group attached directly to the iron center, and a distal histidine group on the opposite face, not bonded to the iron.

Many functional models of myoglobin have been studied. One of the most important are that of picket fence porphyrin by James Collman. This model was used to show the importance of the distal prosthetic group. It serves three functions:

  1. to form hydrogen bonds with the dioxygen moiety, increasing the O2 binding constant
  2. to prevent the binding of carbon monoxide, whether from within or without the body. Carbon monoxide binds to iron in an end-on fashion, and is hindered by the presence of the distal histidine, which forces it into a bent conformation. CO binds to heme 23,000 times better than O2, but only 200 times better in hemoglobin and myoglobin. Oxygen binds in a bent fashion, which can fit with the distal histidine.[18]
  3. to prevent irreversible dimerization of the oxymyoglobin with another deoxymyoglobin species

See also

References

  1. ^ Symbol Report: MB. Retrieved on 2006-05-20.
  2. ^ Takano, T. "Structure of myoglobin refined at 2-0 A resolution. II. Structure of deoxymyoglobin from sperm whale". J. Mol. Biol. 110: 569-584. 
  3. ^ 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. 
  4. ^ 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. 
  5. ^ globin, with user query added. NCBI. Retrieved on 2006-05-20.
  6. ^ ST1818 hypothetical myoglobin [Sulfolobus tokodaii str. 7 GeneID: 1459874 Locus tag: ST1818]. NCBI (03-Dec-2005). Retrieved on 2006-05-20.
  7. ^ glbN Probable hemoglobin glbN [Mycobacterium tuberculosis H37Rv GeneID: 886402 Locus tag: Rv1542c]. NCBI (21-Mar-2006). Retrieved on 2006-05-20.
  8. ^ 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. 
  9. ^ 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. 
  10. ^ Wu, G; Wainwright LM, Poole RK (2003). "Microbial globins". Adv Microb Physiol 47: 255-310. PMID 14560666. 
  11. ^ 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. 
  12. ^ 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. 
  13. ^ 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. 
  14. ^ The Nobel Prize in Chemistry 1962
  15. ^ McGee, H: "On Food and Cooking: The Science and Lore of the Kitchen, page 148. Scribner: New York, 2004. ISBN 0-684-80001-2
  16. ^ 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. 
  17. ^ 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. 
  18. ^ J. P. Collman, J. I. Brauman, T. R. Halbert, and K. S. Suslick (1976). "Nature of Oxygen and Carbon Monoxide Binding to Metalloporphyrins and Heme Proteins". Proceedings of the National Academy of Sciences of the United States of America 73 (10): 3333-3337. 

Further reading

  • J. P. Collman, R. Boulatov, C. J. Sunderland and L. Fu (2004). "Functional Analogues of Cytochrome c Oxidase, Myoglobin, and Hemoglobin". Chem. Rev. 104 (2): 561-588. DOI:10.1021/cr0206059. 

External links


 
 

Join the WikiAnswers Q&A community. Post a question or answer questions about "myoglobin" at WikiAnswers.

 

Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
Food and Fitness. Food and Fitness: A Dictionary of Diet and Exercise. Copyright © 1997, 2003 by Oxford University Press. All rights reserved.  Read more
Sports Science and Medicine. The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved.  Read more
Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/  Read more
Veterinary Dictionary. The Veterinary Dictionary. Copyright © 2007 by Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Myoglobin" Read more

Search for answers directly from your browser with the FREE Answers.com Toolbar!  
Click here to download now. 

Get Answers your way! Check out all our free tools and products.

On this page:   E-mail   print Print  Link  

 

Keep Reading

Mentioned In: