1d6s

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spinqualitylabelsall models 1d6s, resolution 2.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

CRYSTAL STRUCTURE OF THE K41A MUTANT OF O-ACETYLSERINE SULFHYDRYLASE COMPLEXED IN EXTERNAL ALDIMINE LINKAGE WITH METHIONINE

Overview

Covalent binding of L-methionine as an external aldimine to the pyridoxal, 5'-phosphate-cofactor in the K41A mutant of O-acetylserine sulfhydrylase, from Salmonella typhimurium induces a large conformational change in the, protein. Methionine mimics the action of the substrate O-acetyl-L-serine, during catalysis. The alpha-carboxylate moiety of L-methionine in external, aldimine linkage with the active site pyridoxal 5'-phosphate forms a, hydrogen bonding network to the "asparagine-loop" P67-T68-N69-G70 which, adopts a different conformation than in the native protein. The side-chain, nitrogen of Asn69 moves more than 7 A to make a hydrogen bond to the, alpha-carboxylate group of the inhibitor. As the external aldimine is, formed, the PLP tilts by 13 degrees along its longitudinal axis such that, C4' moves toward the entrance to the active site and the side-chain of the, methionine is directed toward the active site entrance. The local, rearrangement acts as a trigger to induce a large global conformational, change in the protein. A subdomain comprised of beta-strand 4, alpha-helix, 3, beta-strand 5 and alpha-helix 4 moves towards the active site by a, rotation of 7 degrees. This subdomain movement results in a reduction of, the severe twist of its central beta-sheet and reduces the active site, entrance to a small hole, giving access only to small molecules like, sulfide, the second substrate, or acetate, the first product.

About this Structure

1D6S is a Single protein structure of sequence from Salmonella typhimurium with MET and PLP as ligands. Active as Cysteine synthase, with EC number 2.5.1.47 Full crystallographic information is available from OCA.

Reference

Ligand binding induces a large conformational change in O-acetylserine sulfhydrylase from Salmonella typhimurium., Burkhard P, Tai CH, Ristroph CM, Cook PF, Jansonius JN, J Mol Biol. 1999 Aug 27;291(4):941-53. PMID:10452898

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