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O-ACETYLSERINE SULFHYDRYLASE FROM SALMONELLA TYPHIMURIUM

Overview

The last step in cysteine biosynthesis in enteric bacteria is catalyzed by, the pyridoxal 5'-phosphate-dependent enzyme O-acetylserine sulfhydrylase., Here we report the crystal structure at 2.2 A resolution of the A-isozyme, of O-acetylserine sulfhydrylase isolated from Salmonella typhimurium., O-acetylserine sulfhydrylase shares the same fold with tryptophan, synthase-beta from Salmonella typhimurium but the sequence identity level, is below 20%. There are some major structural differences: the loops, providing the interface to the alpha-subunit in tryptophan synthase-beta, and two surface helices of tryptophan synthase-beta are missing in, O-acetylserine sulfhydrylase. The hydrophobic channel for indole transport, from the alpha to the beta active site of tryptophan synthase-beta is, not, unexpectedly, also absent in O-acetylserine sulfhydrylase. The dimer, interface, on the other hand, is more or less conserved in the two, enzymes. The active site cleft of O-acetylserine sulfhydrylase is wider, and therefore more exposed to the solvent. A possible binding site for the, substrate O-acetylserine is discussed.

About this Structure

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

Reference

Three-dimensional structure of O-acetylserine sulfhydrylase from Salmonella typhimurium., Burkhard P, Rao GS, Hohenester E, Schnackerz KD, Cook PF, Jansonius JN, J Mol Biol. 1998;283(1):121-33. PMID:9761678

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