This domain is functionally uncharacterised. It is found as the periplasmic domain of the bacterial protein kinase PknH [1]. The domain is also found in isolation in numerous proteins, for example the lipoproteins lpqQ, lprH, lppH and lpqA from M. tuberculosis. This family of proteins is found in bacteria. Proteins in this family are typically between 214 and 268 amino acids in length. There are two completely conserved C residues that are likely to form a disulphide bond. A second pair of cysteines are less well conserved probably form a second disulphide bond. It seems likely that this domain functions to bind some as yet unknown ligand.

1: An FHA phosphoprotein recognition domain mediates protein EmbR phosphorylation by PknH, a Ser/Thr protein kinase from Mycobacterium tuberculosis. Molle V, Kremer L, Girard-Blanc C, Besra GS, Cozzone AJ, Prost JF; Biochemistry. 2003;42:15300-15309. PMID:14690440