title: Positive control of sulphate reduction in Escherichia coli. The nature of the pleiotropic cysteineless mutants of E. coli K12.
abstract: 1. The function of the wild-type alleles of the pleiotropic mutants cysB and cysE of Escherichia coli was investigated. 2. The wild-type allele cysB(+) is dominant to the mutant allele cysB in stable and transient heterozygotes. 3. The wild-type allele cysE(+) is dominant to the mutant allele cysE, as predicted. 4. Sulphur-starved cultures of cysB or cysE strains contain less than 0.2nmole of free cysteine/mg. dry wt. 5. Complementation in vitro is not observed between extracts of cysB mutants and mutants lacking sulphite reductase only. 6. A scheme, involving positive control of the enzymes of sulphate activation and reduction, is suggested to account for the control of cysteine biosynthesis.
mesh_terms: D000483:Alleles; D003545:Cysteine / Q000032:analysis / Q000096:biosynthesis*; D004794:Enzyme Repression; D004926:Escherichia coli / Q000032:analysis / Q000378:metabolism*; D005796:Genes; D005799:Genes, Dominant; D006579:Heterozygote; D009154:Mutation; D010088:Oxidoreductases; D013431:Sulfates / Q000378:metabolism*; D013460:Sulfur Isotopes
chemical_list: D013431:Sulfates; D013460:Sulfur Isotopes; D010088:Oxidoreductases; D003545:Cysteine