1w3u

From Proteopedia

Revision as of 15:19, 5 November 2007

CRYSTAL STRUCTURE OF PHOSPHOSERINE AMINOTRANSFERASE FROM BACILLUS CIRCULANS VAR. ALKALOPHILUS

Overview

The crystal structure of the vitamin B(6)-dependent enzyme phosphoserine, aminotransferase from the obligatory alkaliphile Bacillus alcalophilus has, been determined at 1.08 A resolution. The model was refined to an R-factor, of 11.7% (R(free) = 13.9%). The enzyme displays a narrow pH optimum of, enzymatic activity at pH 9.0. The final structure was compared to the, previously reported structure of the mesophilic phosphoserine, aminotransferase from Escherichia coli and to that of phosphoserine, aminotransferase from a facultative alkaliphile, Bacillus circulans subsp., alkalophilus. All three enzymes are homodimers with each monomer, comprising a two-domain architecture. Despite the high structural, similarity, the alkaliphilic representatives possess a set of distinctive, structural features. Two residues directly interacting with, pyridoxal-5'-phosphate are replaced, and an additional hydrogen bond to, the O3' atom of the cofactor is present in alkaliphilic phosphoserine, aminotransferases. The number of hydrogen bonds and hydrophobic, interactions at the dimer interface is increased. Hydrophobic interactions, between the two domains in the monomers are enhanced. Moreover, the number, of negatively charged amino acid residues increases on the, solvent-accessible molecular surface and fewer hydrophobic residues are, exposed to the solvent. Further, the total amount of ion pairs and ion, networks is significantly reduced in the Bacillus enzymes, while the total, number of hydrogen bonds is increased. The mesophilic enzyme from, Escherichia coli contains two additional beta-strands in a surface loop, with a third beta-strand being shorter in the structure. The identified, structural features are proposed to be possible factors implicated in the, alkaline adaptation of phosphoserine aminotransferase.

About this Structure

1W3U is a Single protein structure of sequence from Bacillus circulans with PLP and GOL as ligands. Active as Phosphoserine transaminase, with EC number 2.6.1.52 Structure known Active Site: AC1. Full crystallographic information is available from OCA.

Reference

Enzyme adaptation to alkaline pH: atomic resolution (1.08 A) structure of phosphoserine aminotransferase from Bacillus alcalophilus., Dubnovitsky AP, Kapetaniou EG, Papageorgiou AC, Protein Sci. 2005 Jan;14(1):97-110. PMID:15608117

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