title: The cysteine synthase complex from plants. Mitochondrial serine acetyltransferase from Arabidopsis thaliana carries a bifunctional domain for catalysis and protein-protein interaction.
abstract: Serine acetyltransferase (SAT) catalyzes the rate-limiting step of cysteine biosynthesis in bacteria and plants and functions in association with O-acetylserine (thiol) lyase (OAS-TL) in the cysteine synthase complex. Very little is known about the structure and catalysis of SATs except that they share a characteristic C-terminal hexapeptide-repeat domain with a number of enzymatically unrelated acyltransferases. Computational modeling of this domain was performed for the mitochondrial SAT isoform from Arabidopsis thaliana, based on crystal structures of bacterial acyltransferases. The results indicate a left-handed parallel beta-helix consisting of beta-sheets alternating with turns, resulting in a prism-like structure. This model was challenged by site-directed mutagenesis and tested for a suspected dual function of this domain in catalysis and hetero-oligomerization. The bifunctionality of the SAT C-terminus in transferase activity and interaction with OAS-TL is demonstrated and discussed with respect to the putative role of the cysteine synthase complex in regulation of cysteine biosynthesis.
authors.affiliation: Institut für Pflanzengenetik und Kulturpflanzenforschung, Gatersleben, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Wirtz
authors.forename: O
authors.initials: O
authors.lastname: Berkowitz
authors.forename: M
authors.initials: M
authors.lastname: Droux
authors.forename: R
authors.initials: R
authors.lastname: Hell
mesh_terms: D000123:Acetyltransferases / Q000737:chemistry*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D019757:Carbon-Oxygen Lyases / Q000378:metabolism; D002384:Catalysis; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D003547:Cysteine Synthase / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D004252:DNA Mutational Analysis; D016208:Databases, Factual; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000201:enzymology; D005816:Genetic Complementation Test; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology*; D008957:Models, Genetic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes; D016297:Mutagenesis, Site-Directed; D010944:Plants / Q000201:enzymology*; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D051050:Serine O-Acetyltransferase; D012984:Software; D020798:Two-Hybrid System Techniques
chemical_list: D009097:Multienzyme Complexes; D029701:Saccharomyces cerevisiae Proteins; D000123:Acetyltransferases; D051050:Serine O-Acetyltransferase; D003547:Cysteine Synthase; C103381:MET17 protein, S cerevisiae; C018725:O-acetylhomoserine (thiol)-lyase; D019757:Carbon-Oxygen Lyases