Chlorocruorin

Chlorocruorin (from Greek khlōros "green" + Latin cruor "blood"), sometimes known as giant hemoglobin with erythrocruorin, is an oxygen-binding hemeprotein present in the blood plasma of four families of annelids, particularly certain marine polychaetes.[1][2][3] Its affinity for oxygen is weaker than that of most hemoglobins. A dichromatic compound, chlorocruorin is noted for appearing green in dilute solutions, though it appears light red when found in concentrated solutions.[4][5][6]

Heme in chlorocruorin, the source of its unique green color.

The only significant difference between chlorocruorin and erythrocruorin is that chlorocruorin carries an abnormal heme group structure. Both contain many 16-17 kDa myoglobin-like subunits arranged in a giant complex of over a hundred subunits with interlinking proteins as well with a total weight exceeding 3600 kDa. [7] This enormous macromolecule is typically found free floating in the plasma, and not contained within red blood cells.[7][8]

Structure

Giant hemoglobin is composed of multiple heme-containing globin chains and linker (InterPro: IPR031639) chains. Each species have different amounts of genes for these chains. For example, while a Lamellibrachia sp. has four kinds of globin chains and two kinds of linker chains, Sabella spallanzanii has three globin chains and three linker chains.[7] The exact stoichiometric ratios and arrangement is unknown, but is thought to resemble that of erythocrorins.

References
  1. H. Munro Fox (1 April 1933). "The Blood Circulation of Animals Possessing Chlorocruorin". Proceedings of the Royal Society B. 112 (779): 479–495. doi:10.1098/rspb.1938.0042. JSTOR 81599.
  2. R. F. Ewer; H. Munro Fox (9 August 1940). "On the Function of Chlorocruorin". Proceedings of the Royal Society B. 129 (855): 137–153. doi:10.1098/rspb.1940.0033. JSTOR 82389.
  3. D.W. Ewer (1941). "The blood systems of Sabella and Spirographis". Quarterly Journal of Microscopical Science. 82 (s2): 587–619. Retrieved 1 May 2010.
  4. H. Munro Fox (1 February 1926). "Chlorocruorin: A Pigment Allied to Haemoglobin". Proceedings of the Royal Society B. 99 (696): 199–220. doi:10.1098/rspb.1926.0008. JSTOR 81088.
  5. H. Munro Fox (1 September 1932). "The Oxygen Affinity of Chlorocruorin". Proceedings of the Royal Society B. 111 (772): 356–363. doi:10.1098/rspb.1932.0060. JSTOR 81716.
  6. H. Munro Fox (19 October 1949). "On Chlorocruorin and Haemoglobin". Proceedings of the Royal Society B. 136 (884): 378–388. doi:10.1098/rspb.1949.0031. JSTOR 82565. PMID 18143368. S2CID 6133526.
  7. Pallavicini A, Negrisolo E, Barbato R, et al. (July 2001). "The primary structure of globin and linker chains from the chlorocruorin of the polychaete Sabella spallanzanii". J. Biol. Chem. 276 (28): 26384–90. doi:10.1074/jbc.M006939200. PMID 11294828.
  8. Lamy JN, Green BN, Toulmond A, Wall JS, Weber RE, Vinogradov SN (19 December 1996). "Giant Hexagonal Bilayer Hemoglobins". Chem Rev. 96 (8): 3113–3124. doi:10.1021/cr9600058. PMID 11848854.


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