This is a large and diverse family of putative metal chaperones that can be separated into up to 15 subgroups. In addition to known roles in cobalamin biosynthesis [1] and the activation of the Fe-type nitrile hydratase, this family is also known to be involved in the response to zinc limitation. The CobW subgroup involved in cobalamin synthesis represents only a small sub-fraction of the family [2].

1: Nucleotide sequence and genetic analysis of a 13.1-kilobase-pair Pseudomonas denitrificans DNA fragment containing five cob genes and identification of structural genes encoding Cob(I)alamin adenosyltransferase, cobyric acid synthase, and bifunctional cob Crouzet J, Levy-Schil S, Cameron B, Cauchois L, Rigault S, Rouyez MC, Blanche F, Debussche L, Thibaut D; J Bacteriol 1991;173:6074-6087. PMID:1655697

2: A subset of the diverse COG0523 family of putative metal chaperones is linked to zinc homeostasis in all kingdoms of life. Haas CE, Rodionov DA, Kropat J, Malasarn D, Merchant SS, de Crecy-Lagard V; BMC Genomics. 2009;10:470. PMID:19822009