title: Characterization of the CysB protein of Klebsiella aerogenes: direct evidence that N-acetylserine rather than O-acetylserine serves as the inducer of the cysteine regulon.
abstract: The cysB gene of Klebsiella aerogenes has been cloned, sequenced and shown to complement the cysteine auxotrophic phenotype of Escherichia coli cysB mutants. The K. aerogenes cysB gene is predicted to encode a protein of 324 amino acid residues that shares approx. 95% sequence similarity with the Salmonella typhimurium and E. coli CysB proteins. Gel-retardation assays demonstrate that the purified protein binds to DNA fragments containing either the K. aerogenes cysb promoter or the S. typhimurium cysJIH promoter. Acetylserine enhances CysB binding to the cysJIH promoter fragment while diminishing its binding to the cysB promoter fragment. Fluorescence-emission-spectroscopy measurements suggest strongly that N-acetylserine binds to CysB apoprotein but that O-acetylserine does not, and support the notion that N-acetylserine is the physiological inducer of cysteine biosynthesis.
authors.affiliation: Department of Chemistry, University of York, U.K.
authors.forename: A S
authors.initials: AS
authors.lastname: Lynch
authors.forename: R
authors.initials: R
authors.lastname: Tyrrell
authors.forename: S J
authors.initials: SJ
authors.lastname: Smerdon
authors.forename: G S
authors.initials: GS
authors.lastname: Briggs
authors.forename: A J
authors.initials: AJ
authors.lastname: Wilkinson
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D003545:Cysteine / Q000096:biosynthesis* / Q000235:genetics; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D007711:Klebsiella pneumoniae / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D018085:Regulon; D012486:Salmonella typhimurium / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C062886:CysB protein, Bacteria; C489265:CysB protein, Salmonella typhimurium; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D012694:Serine; C043943:O-acetylserine; D003545:Cysteine; C012162:N-acetylserine