Polymerase and Histidinol Phosphatase domain of Histidinol phosphate phosphatase (HisPPase) AMP bound
The PHP domain of this HisPPase family has an unknown function. It has a second domain inserted in the middle that binds adenosine 5-monophosphate (AMP). 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. HisPPase catalyzes the eighth step of histidine biosynthesis, in which L-histidinol phosphate undergoes dephosphorylation to give histidinol. 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 the 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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