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Information about Myoglobin

Myoglobin

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 modificationsglycation?[8]
phosphorylation in whales?[9]
Other names:myoglobin-like proteins in microorganisms[10]
Molecular interactionsoxygen,
heme,
carbon monoxide,
nitric oxide
related articles:X-ray crystallography,
Secondary structure


Enlarge picture
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

Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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A hemoprotein (also haemoprotein), or heme protein, is a metalloprotein containing a heme prosthetic group, either covalently or noncovalently bound to the protein itself.
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2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol−1
2nd: 3388.3 kJmol−1
3rd: 5300.5 kJmol−1

Atomic radius 60 pm
Atomic radius (calc.
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disease is an abnormal condition of an organism that impairs bodily functions. In human beings, "disease" is often used more broadly to refer to any condition that causes discomfort, dysfunction, distress, social problems, and/or death to the person afflicted, or similar problems
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The kidneys are organs that filter wastes (such as urea) from the blood and excrete them, along with water, as urine. The medical field that studies the kidneys and diseases of the kidney is called nephrology[1].
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Vasospasm
Classification & external resources

ICD-9 443.9

Vasospasm refers to a condition in which blood vessels spasm, leading to vasoconstriction. This can lead to tissue ischemia and death (necrosis).
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For the journal, see .
A taxon (plural taxa), or taxonomic unit, is a name designating an organism or group of organisms. A taxon is assigned a rank and can be placed at a particular level in a systematic hierarchy reflecting evolutionary
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phylum (Greek Φῦλον plural: Φῦλα phyla) is a taxon in the rank below kingdom and above class.
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Archaea
Woese, Kandler & Wheelis, 1990

Phyla

Crenarchaeota
Euryarchaeota
Korarchaeota
Nanoarchaeota
ARMAN
The Archaea (
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There are about 210 known distinct human cell types.

Keratinizing epithelial cells

  • Epidermal keratinocyte (differentiating epidermal cell)
  • Epidermal basal cell (stem cell)
  • Keratinocyte of fingernails and toenails
  • Nail bed basal cell (stem cell)

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MUSCLE (multiple sequence comparison by log-expectation) is public domain, multiple sequence alignment software for protein and nucleotide sequences.
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Cytoplasm is a gelatinous, semi-transparent fluid that fills most cells. Eukaryotic cells contain a nucleus that is kept separate from the cytoplasm by a double membrane layer. The cytoplasm has three major elements; the cytosol, organelles and inclusions.
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Covalent bonding is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or between atoms and other covalent bonds.
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Phosphorylation is the addition of a phosphate (PO4) group to a protein molecule or a small molecule. Another way to define it would be the introduction of a phosphate group into an organic molecule.
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molecule is defined as a sufficiently stable electrically neutral group of at least two atoms in a definite arrangement held together by strong chemical bonds.[1][2] In organic chemistry and biochemistry, the term molecule
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2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol−1
2nd: 3388.3 kJmol−1
3rd: 5300.5 kJmol−1

Atomic radius 60 pm
Atomic radius (calc.
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A heme or haem is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin. Not all porphyrins contain iron, but a substantial fraction of porphyrin-containing metalloproteins have heme as
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Carbon monoxide, with the chemical formula CO, is a colorless, odorless, and tasteless gas. It is the product of the incomplete combustion of carbon-containing compounds, notably in internal-combustion engines.
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Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of mammals including humans and is an extremely important intermediate in the chemical industry.
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X-ray crystallography is the science of determining the arrangement of atoms within a crystal from the manner in which a beam of X-rays is scattered from the electrons within the crystal.
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secondary structure is the general three-dimensional form of local segments of biopolymers such as proteins and nucleic acids (DNA/RNA). It does not, however, describe specific atomic positions in three-dimensional space, which are considered to be tertiary structure.
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In biochemistry and chemistry, the tertiary structure of a protein or any other macromolecule is its three-dimensional structure, as defined by the atomic coordinates.[1]

Relationship to primary sequence


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Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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amino acid is a molecule that contains both amine and carboxyl functional groups. In biochemistry, this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent.
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A heme or haem is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin. Not all porphyrins contain iron, but a substantial fraction of porphyrin-containing metalloproteins have heme as
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3, 4, 6
(amphoteric oxide)
Electronegativity 1.83 (Pauling scale)
Ionization energies
(more) 1st: 762.5 kJmol−1
2nd: 1561.9 kJmol−1
3rd: 2957 kJmol−1

Atomic radius 140 pm
Atomic radius (calc.
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porphyrin is a heterocyclic macrocycle derived from four pyrrole-like subunits interconnected via their α carbon atoms via methine bridges (=CH-). The macrocycle, therefore, is a highly conjugated system, and is consequently deeply coloured—the name porphyrin
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A prosthetic group is a non-protein (non-amino acid) component of a conjugated protein. The prosthetic group may be organic (such as a vitamin, sugar, or lipid) or inorganic (such as a metal ion). Prosthetic groups usually bond covalently to their protein.
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An apoprotein is a protein without its characteristic prosthetic group.

Apoproteins are lipid-binding proteins present in chylomicrons, absorbed by Enterocytes within the small intestines and colonocytes in the colon.
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