This is a family of bacterial proteins that have a nucleotidyltransferase fold. The fold-prediction is backed up by conservation of three highly characteristic sequence motifs found in all other nucleotidyl transferases: i) pDhDhhh(h/p), where p is a polar residue and h is a hydrophobic residue; ii) upstream of the first, a GG/S; iii) a conserved D/E in a hydrophobic surround. In the classification of nucleotidyltransferases proposed in [1] this is a group XVIII NTP-transferase. Many of these sequences were classified in the COG database as COG5397. The exact function is not known.

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