1k7f
From Proteopedia
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CRYSTAL STRUCTURE OF WILD-TYPE TRYPTOPHAN SYNTHASE COMPLEXED WITH N-[1H-INDOL-3-YL-ACETYL]VALINE ACID
Overview
Tryptophan synthase is a bifunctional alpha(2)beta(2) complex catalyzing the last two steps of l-tryptophan biosynthesis. The natural substrates of the alpha-subunit indole- 3-glycerolphosphate and glyceraldehyde-3-phosphate, and the substrate analogs indole-3-propanolphosphate and dl-alpha-glycerol-3-phosphate are allosteric effectors of the beta-subunit activity. It has been shown recently, that the indole-3-acetyl amino acids indole-3-acetylglycine and indole-3-acetyl-l-aspartic acid are both alpha-subunit inhibitors and beta-subunit allosteric effectors, whereas indole-3-acetyl-l-valine is only an alpha-subunit inhibitor (Marabotti, A., Cozzini, P., and Mozzarelli, A. (2000) Biochim. Biophys. Acta 1476, 287-299). The crystal structures of tryptophan synthase complexed with indole-3-acetylglycine and indole-3-acetyl-l-aspartic acid show that both ligands bind to the active site such that the carboxylate moiety is positioned similarly as the phosphate group of the natural substrates. As a consequence, the residues of the alpha-active site that interact with the ligands are the same as observed in the indole 3-glycerolphosphate-enzyme complex. Ligand binding leads to closure of loop alphaL6 of the alpha-subunit, a key structural element of intersubunit communication. This is in keeping with the allosteric role played by these compounds. The structure of the enzyme complex with indole-3-acetyl-l-valine is quite different. Due to the hydrophobic lateral chain, this molecule adopts a new orientation in the alpha-active site. In this case, closure of loop alphaL6 is no longer observed, in agreement with its functioning only as an inhibitor of the alpha-subunit reaction.
About this Structure
1K7F is a Protein complex structure of sequences from Salmonella typhimurium with and as ligands. Active as Tryptophan synthase, with EC number 4.2.1.20 Full crystallographic information is available from OCA.
Reference
Crystal structures of a new class of allosteric effectors complexed to tryptophan synthase., Weyand M, Schlichting I, Marabotti A, Mozzarelli A, J Biol Chem. 2002 Mar 22;277(12):10647-52. Epub 2001 Dec 26. PMID:11756456
Page seeded by OCA on Thu Feb 21 13:30:56 2008
