Crystal Structure of Monofunctional Histidinol Phosphate Phosphatase from Thermus thermophilus HB8

Abstract

Monofunctional histidinol phosphate phosphatase from Thermus thermophilus HB8, which catalyzes the dephosphorylation of l-histidinol phosphate, belongs to the PHP family, together with the PHP domain of bacterial DNA polymerase III and family X DNA polymerase. We have determined the structures of the complex with a sulfate ion, the complex with a phosphate ion, and the unliganded form at 1.6, 2.1, and 1.8 A resolution, respectively. The enzyme exists as a tetramer, and the subunit consists of a distorted (betaalpha)7 barrel with one linker and one C-terminal tail. Three metal sites located on the C-terminal side of the barrel are occupied by Fe1, Fe2, and Zn ions, respectively, forming a trinuclear metal center liganded by seven histidines, one aspartate, one glutamate, and one hydroxide with two Fe ions bridged by the hydroxide. In the complexes, the sulfate or phosphate ion is coordinated to three metal ions, resulting in octahedral, trigonal bipyramidal, and tetrahedral geometries around the Fe1, Fe2, and Zn ions, respectively. The ligand residues are derived from the four motifs that characterize the PHP family and from two motifs conserved in histidinol phosphate phosphatases. The (betaalpha)7 barrel and the metal cluster are closely related in nature and architecture to the (betaalpha)8 barrel and the mononuclear or dinuclear metal center in the amidohydrolase superfamily, respectively. The coordination behavior of the phosphate ion toward the metal center supports the mechanism in which the bridging hydroxide makes a direct attack on the substrate phosphate tridentately bound to the two Fe ions and Zn ion to hydrolyze the phosphoester bond.

Crystal structures of YwqE from Bacillus subtilis and CpsB from Streptococcus pneumoniae, unique metal-dependent tyrosine phosphatases

“…The flexible loop I and II are indicated with green and black dotted circles, respectively, and the channels formed by these loops are indicated by black arrows. sweet potato purple acid phosphatase (Schenk et al, 2005), monofunctional histidinol phosphate phosphatase from Thermus thermophilus HB8 (Omi et al, 2007), and amidohydrolase superfamily members (Seibert and Raushel, 2005). In the structure of B. subtilis YwqE-PO 3À 4 , the phosphate ion is liganded to all three metal ions via its oxygen atoms.…”

Streptococcus pneumoniae Phosphotyrosine Phosphatase CpsB and Alterations in Capsule Production Resulting from Changes in Oxygen Availability

“…Unlike low-molecular-weight phosphotyrosine phosphatases, which utilize a catalytic cysteine residue in their active sites (30,31), PHP proteins utilize a series of coordinated histidine and aspartic acid residues in their catalysis (15,17,29,(32)(33)(34). These residues are coordinated through four characteristic PHP motifs (29).…”

An atypical phosphodiesterase capable of degrading haloalkyl phosphate diesters from Sphingobium sp. strain TCM1

“…The PHP motif is predicted to be involved in metal-dependent phosphoester bond hydrolysis 24 , and structurally characterized enzymes of the PHP superfamily contain a trinuclear metal center in the active site 28–31 . Sb -PDE and several homologous proteins have the four conserved motifs 24 that have been predicted to be involved in the formation of the metal binding sites (Fig.…”