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Publication Abstract from PubMed

The biosynthesis of cysteine in bacteria and plants is carried out by a two-step pathway, catalyzed by serine acetyltransferase (SAT) and O-acetylserine sulfhydrylase (OASS; O-acetylserine [thiol] lyase). The aerobic form of OASS forms a tight bienzyme complex with SAT in vivo, termed cysteine synthase. We have determined the crystal structure of OASS in complex with a C-terminal peptide of SAT required for bienzyme complex formation. The binding site of the peptide is at the active site of OASS, and its C-terminal carboxyl group occupies the same anion binding pocket as the alpha-carboxylate of the O-acetylserine substrate of OASS. These results explain the partial inhibition of OASS by SAT on complex formation as well as the competitive dissociation of the complex by O-acetylserine.

The active site of O-acetylserine sulfhydrylase is the anchor point for bienzyme complex formation with serine acetyltransferase.,Huang B, Vetting MW, Roderick SL J Bacteriol. 2005 May;187(9):3201-5. PMID:15838047^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.