Siderocalin

Siderocalin is a protein that is produced by the body in response to bacterial infection. During an infection, bacteria produce iron-chelators called siderophores which are used for 'stealing' iron from the host. E.coli for example produces catecholate type of siderophore called Enterobactin (also known as enterochelin) that binds iron(III) strongly (binding constant K approximately 10⁵² M^-1). Siderocalin has been shown to bind ferric-catecholates, one of which is enterobactin [D.H. Goetz, M.A. Holmes, N. Borregaard, M.E. Bluhm, M.E., K.N. Raymond, R.K. Strong. "Mol. Cell", 2002, 10, 1033–1043.] and hence prevents the iron from being delivered to the bacteria. It is thus can be seen as part of an innate immune response for protection against infection.

Origin

Siderocalins are formerly known as lipocalins, which are small extracellular proteins. They bind to retinol (also known as vitamin A) and are involved in the transport of retinol [M. Newcomer. "Structure", 2005,13 (1), 1-2] . It is only in the recent years that lipocalin has been recognised as a scavenger of siderophores. This results in the new name siderocalin (sidero for "sidero"phore, calin for lipo"calin").

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