Erythrocruorin Explained

Erythrocruorin (from Greek eruthros "red" + Latin cruor "blood"), and the similar chlorocruorin (from Greek khlōros "green" + Latin cruor "blood"), are large oxygen-carrying hemeprotein complexes, which have a molecular mass greater than 3.5 million daltons. Both are sometimes called giant hemoglobin or hexagonal bilayer haemoglobin. They are found in many annelids and arthropods (including some insects).^[1]

Chlorocruorin is particularly found in certain marine polychaetes.^{[2] [3] [4]}

Structure

Two structures of erythrocruorin have been resolved. The protein is a highly symmetric assembly made from heme-binding globins and unique linker proteins.^{[5] [6]}

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. ^[6]

Giant hemoglobin is composed of multiple heme-containing globin chains and linker 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.^[6] The exact stoichiometric ratios and arrangement is unknown, but is thought to resemble that of erythocrorins.

Properties

Erythrocruorin has a weaker affinity for oxygen 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.^{[7] [8] [9]}

This enormous macromolecule is typically found free floating in the plasma, and not contained within red blood cells.^[10]

External links

• • • RSDB Molecule of the Month: 159 Erythrocruorin

Notes and References

1. Ruggiero Bachega JF, Vasconcelos Maluf F, Andi B, D'Muniz Pereira H, Falsarella Carazzollea M, Orville AM, Tabak M, Brandão-Neto J, Garratt RC, Horjales Reboredo E . 6 . The structure of the giant haemoglobin from Glossoscolex paulistus . Acta Crystallographica. Section D, Biological Crystallography . 71 . Pt 6 . 1257–71 . June 2015 . 26057666 . 10.1107/S1399004715005453 .
2. H. Munro Fox. The Blood Circulation of Animals Possessing Chlorocruorin. Proceedings of the Royal Society B. 112. 779. 479–495. 1 April 1933. 10.1098/rspb.1938.0042. 81599. free.
3. R. F. Ewer. H. Munro Fox. On the Function of Chlorocruorin. Proceedings of the Royal Society B. 129. 855. 137–153. 9 August 1940. 10.1098/rspb.1940.0033. 82389. 1940RSPSB.129..137E . free.
4. D.W. Ewer. The blood systems of Sabella and Spirographis. Quarterly Journal of Microscopical Science. 82. s2. 587–619. 1941. 1 May 2010.
5. Royer WE, Strand K, van Heel M, Hendrickson WA . Structural hierarchy in erythrocruorin, the giant respiratory assemblage of annelids . Proceedings of the National Academy of Sciences of the United States of America . 97 . 13 . 7107–11 . June 2000 . 10860978 . 16507 . 10.1073/pnas.97.13.7107 . 2000PNAS...97.7107R . free .
6. Pallavicini A, Negrisolo E, Barbato R, Dewilde S, Ghiretti-Magaldi A, Moens L, Lanfranchi G . The primary structure of globin and linker chains from the chlorocruorin of the polychaete Sabella spallanzanii . The Journal of Biological Chemistry . 276 . 28 . 26384–90 . July 2001 . 11294828 . 10.1074/jbc.M006939200 . free .
7. H. Munro Fox. Chlorocruorin: A Pigment Allied to Haemoglobin. Proceedings of the Royal Society B. 99. 696. 199–220. 1 February 1926. 10.1098/rspb.1926.0008. 81088. free.
8. H. Munro Fox. The Oxygen Affinity of Chlorocruorin. Proceedings of the Royal Society B. 111. 772. 356–363. 1 September 1932. 10.1098/rspb.1932.0060. 81716. free.
9. H. Munro Fox. On Chlorocruorin and Haemoglobin. Proceedings of the Royal Society B. 136. 884. 378–388. 19 October 1949. 82565. 10.1098/rspb.1949.0031. 18143368. 1949RSPSB.136..378F . 6133526.
10. Lamy JN, Green BN, Toulmond A, Wall JS, Weber RE, Vinogradov SN. Giant Hexagonal Bilayer Hemoglobins. Chem Rev. 96. 8. 3113–3124. 19 December 1996. 11848854. 10.1021/cr9600058.