2sfp
From Proteopedia
ALANINE RACEMASE WITH BOUND PROPIONATE INHIBITOR
Overview
The structure of alanine racemase from Bacillus stearothermophilus with the inhibitor propionate bound in the active site was determined by X-ray crystallography to a resolution of 1.9 A. The enzyme is a homodimer in solution and crystallizes with a dimer in the asymmetric unit. Both active sites contain a pyridoxal 5'-phosphate (PLP) molecule in aldimine linkage to Lys39 as a protonated Schiff base, and the pH-independence of UV-visible absorption spectra suggests that the protonated PLP-Lys39 Schiff base is the reactive form of the enzyme. The carboxylate group of propionate bound in the active site makes numerous interactions with active-site residues, defining the substrate binding site of the enzyme. The propionate-bound structure therefore approximates features of the Michaelis complex formed between alanine racemase and its amino acid substrate. The structure also provides evidence for the existence of a carbamate formed on the side-chain amino group of Lys129, stabilized by interactions with one of the residues interacting with the carboxylate group of propionate, Arg136. We propose that this novel interaction influences both substrate binding and catalysis by precisely positioning Arg136 and modulating its charge.
About this Structure
2SFP is a Single protein structure of sequence from Geobacillus stearothermophilus. Full crystallographic information is available from OCA.
Reference
Structure of a Michaelis complex analogue: propionate binds in the substrate carboxylate site of alanine racemase., Morollo AA, Petsko GA, Ringe D, Biochemistry. 1999 Mar 16;38(11):3293-301. PMID:10079072 Page seeded by OCA on Sun May 4 17:18:15 2008
