ThiS (thiaminS) is a 66 aa protein involved in sulphur transfer Swiss:O32583. ThiS is coded in the thiCEFSGH operon in E. coli. This family of proteins have two conserved Glycines at the COOH terminus. Thiocarboxylate is formed at the last G in the activation process. Sulphur is transferred from ThiI to ThiS in a reaction catalysed by IscS [1]. MoaD, Swiss:P30748 a protein involved sulphur transfer in molybdopterin synthesis, is about the same length and shows limited sequence similarity to ThiS. Both have the conserved GG at the COOH end.

1: The iscS gene in Escherichia coli is required for the biosynthesis of 4-thiouridine, thiamin, and NAD. Lauhon CT, Kambampati R; J Biol Chem 2000;275:20096-20103. PMID:10781607