title: Cysteine biosynthesis in Lactobacillus casei: identification and characterization of a serine acetyltransferase.
abstract: In bacteria, cysteine can be synthesized from serine by two steps involving an L-serine O-acetyltransferase (SAT) and a cysteine synthase (CysK). While CysK is found in the publicly available annotated genome from Lactobacillus casei ATCC 334, a gene encoding SAT (cysE) is missing. In this study, we found that various strains of L. casei grew in a chemically defined medium containing sulfide as the sole sulfur source, indicating the presence of a serine O-acetyltransferase. The gene lying upstream of cysK is predicted to encode a homoserine trans-succinylase (metA). To study the function of this gene, it was cloned from L. casei FAM18110. The purified, recombinant protein did not acylate L-homoserine in vitro. Instead, it catalyzed the formation of O-acetyl serine from L-serine and acetyl-CoA. Furthermore, the plasmid expressing the L. casei gene complemented an Escherichia coli cysE mutant strain but not an E. coli metA mutant. This clearly demonstrated that the gene annotated as metA in fact encodes the SAT function and should be annotated as cysE.
authors.affiliation: Agroscope, Institute for Food Sciences IFS, 3003 Berne, Switzerland.
authors.forename: Biljana
authors.initials: B
authors.lastname: Bogicevic
authors.affiliation: Agroscope, Institute for Food Sciences IFS, 3003 Berne, Switzerland.
authors.forename: Hélène
authors.initials: H
authors.lastname: Berthoud
authors.affiliation: Agroscope, Institute for Food Sciences IFS, 3003 Berne, Switzerland.
authors.forename: Reto
authors.initials: R
authors.lastname: Portmann
authors.affiliation: Agroscope, Institute for Food Sciences IFS, 3003 Berne, Switzerland.
authors.forename: Tharmatha
authors.initials: T
authors.lastname: Bavan
authors.affiliation: Laboratory of Food Biotechnology, Institute of Food Science and Nutrition, ETH Zürich, 8092 Zürich, Switzerland.
authors.forename: Leo
authors.initials: L
authors.lastname: Meile
authors.affiliation: Agroscope, Institute for Food Sciences IFS, 3003 Berne, Switzerland stefan.irmler@agroscope.admin.ch.
authors.forename: Stefan
authors.initials: S
authors.lastname: Irmler
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism; D003001:Cloning, Molecular; D003470:Culture Media / Q000737:chemistry; D003545:Cysteine / Q000096:biosynthesis*; D003547:Cysteine Synthase / Q000378:metabolism; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000235:genetics; D007780:Lacticaseibacillus casei / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D058977:Molecular Sequence Annotation; D009154:Mutation; D010957:Plasmids; D011994:Recombinant Proteins / Q000378:metabolism; D012694:Serine / Q000031:analogs & derivatives / Q000378:metabolism; D051050:Serine O-Acetyltransferase / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D013455:Sulfur / Q000378:metabolism
chemical_list: D003470:Culture Media; D004269:DNA, Bacterial; D011994:Recombinant Proteins; D012694:Serine; D013455:Sulfur; D000105:Acetyl Coenzyme A; D051050:Serine O-Acetyltransferase; D003547:Cysteine Synthase; C043943:O-acetylserine; D003545:Cysteine
keywords: Lactobacillus casei; cysE; cysteine biosynthesis; serine acetyltransferase