This is a family of bacterial putative uroporphyrinogen-III C-methyltransferase proteins. It forms one of the members of a complex of proteins involved in the biogenesis of the inner membrane in E.coli. Uroporphorphyrin-III C-methyltransferase (HemX) is a single spanning inner membrane protein that regulates the activity of NAD(P)H:glutamyl-tRNA reductase (HemA) in the tetrapyrrole biosynthesis pathway.