1w2i

From Proteopedia

Revision as of 08:18, 3 February 2008

CRYSTAL STRUCTUORE OF ACYLPHOSPHATASE FROM PYROCOCCUS HORIKOSHII COMPLEXED WITH FORMATE

Overview

Acylphosphatases catalyze the hydrolysis of the carboxyl-phosphate bond in, acyl phosphates. Although acylphosphatase-like sequences are found in all, three domains of life, no structure of acylphosphatase has been reported, for bacteria and archaea so far. Here, we report the characterization of, enzymatic activities and crystal structure of an archaeal acylphosphatase., A putative acylphosphatase gene (PhAcP) was cloned from the genomic DNA of, Pyrococcus horikoshii and was expressed in Escherichia coli. Enzymatic, parameters of the recombinant PhAcP were measured using benzoyl phosphate, as the substrate. Our data suggest that, while PhAcP is less efficient, than other mammalian homologues at 25 degrees C, the thermophilic enzyme, is fully active at the optimal growth temperature (98 degrees C) of P., horikoshii. PhAcP is extremely stable; its apparent melting temperature, was 111.5 degrees C and free energy of unfolding at 25 degrees C was 54 kJ, mol(-)(1). The 1.5 A crystal structure of PhAcP adopts an alpha/beta, sandwich fold that is common to other acylphosphatases. PhAcP forms a, dimer in the crystal structure via antiparallel association of strand 4., Structural comparison to mesophilic acylphosphatases reveals significant, differences in the conformation of the L5 loop connecting strands 4 and 5., The extreme thermostability of PhAcP can be attributed to an extensive, ion-pair network consisting of 13 charge residues on the beta sheet of the, protein. The reduced catalytic efficiency of PhAcP at 25 degrees C may be, due to a less flexible active-site residue, Arg20, which forms a salt, bridge to the C-terminal carboxyl group. New insights into catalysis were, gained by docking acetyl phosphate to the active site of PhAcP.

About this Structure

1W2I is a Single protein structure of sequence from Pyrococcus horikoshii with as ligand. Active as Acylphosphatase, with EC number 3.6.1.7 Known structural/functional Site: . Full crystallographic information is available from OCA.

Reference

Crystal structure of a hyperthermophilic archaeal acylphosphatase from Pyrococcus horikoshii--structural insights into enzymatic catalysis, thermostability, and dimerization., Cheung YY, Lam SY, Chu WK, Allen MD, Bycroft M, Wong KB, Biochemistry. 2005 Mar 29;44(12):4601-11. PMID:15779887

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