This family has been suggested to belong to the nucleotidyltransferase superfamily [1]. It occurs at the C-terminus of dephospho-CoA kinase (CoaE) in a number of cases, where it plays a role in the proper folding of the enzyme [2].

1: Comprehensive classification of nucleotidyltransferase fold proteins: identification of novel families and their representatives in human. Kuchta K, Knizewski L, Wyrwicz LS, Rychlewski L, Ginalski K; Nucleic Acids Res. 2009; [Epub ahead of print] PMID:19833706

2: The role of UPF0157 in the folding of M. tuberculosis dephosphocoenzyme A kinase and the regulation of the latter by CTP. Walia G, Kumar P, Surolia A; PLoS One. 2009;4:e7645. PMID:19876400