This family of proteins represents HapK, a protein of unknown function, with two homologues PigK and RedY. The monomer structure of the protein contains a four-stranded anti parallel β-sheet, three α-helices and a short C-terminal tail which it uses for dimer formation []. The surface of HapK has a deep cavity with consists of a kinked helix and a β-four strand. HapK could be involved in prodigiosin biosynthesis, specifically the binding of a bipyrrole intermediate such as HBM or MBM [].
