Polymerase and Histidinol Phosphatase domain of Histidinol phosphate phosphatase
HisPPase catalyzes the eighth step of histidine biosynthesis, in which L-histidinol phosphate undergoes dephosphorylation to produce histidinol. HisPPase can be classified into two types: the bifunctional HisPPase found in proteobacteria that belongs to the DDDD superfamily and the monofunctional Bacillus subtilis type that is a member of the PHP family. The PHP (also called histidinol phosphatase-2/HIS2) domain is associated with several types of DNA polymerases, such as PolIIIA and family X DNA polymerases, stand alone histidinol phosphate phosphatases (HisPPases), and a number of uncharacterized protein families. The PHP domain has four conserved sequence motifs and contains an invariant histidine that is involved in metal ion coordination. The PHP domain of HisPPase is structurally homologous to other members of the PHP family that have a distorted (beta/alpha)7 barrel fold with a trinuclear metal site on the C-terminal side of the barrel.
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