title: Isolation and characterization of cysK mutants of Escherichia coli K12.
abstract: cysK mutants, deficient in O-acetylserine sulphydrylase A [O-acetyl-L-serine acetate-lyase (adding hydrogen-sulphide); EC 4.2.99.8], were isolated as strains resistant to selenite or giving a black colour reaction on bismuth citrate indicator medium. All were resistant to the inhibitor I,2,4-triazole. Four independent mutants were found which possessed lowered levels of O-acetylserine sulphydrylase activity and also partially constitutive levels of NADPH-sulphite reductase [hydrogen-sulphide: NADP+ oxidoreductase; EC I.8.I.2]. Strains containing both a cysE mutation and a cysK mutation lacked the constitutive levels of NADPH-sulphite reductase showing that these levels were due to the in vivo concentration of the inducer, O-acetylserine. The cysK locus was found to be 81% cotransducible with the ptsI gene.
mesh_terms: D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D003547:Cysteine Synthase / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D009154:Mutation; D010088:Oxidoreductases / Q000378:metabolism
chemical_list: D010088:Oxidoreductases; D003547:Cysteine Synthase