title: Positive control in the D-serine deaminase system of Escherichia coli K-12.
abstract: Two new types of D-serine deaminase (Dsdase)-negative mutants have been isolated and characterized. The first fails to synthesize a functional dsdC gene product as a result of dsdC- (regulator negative) mutations. The mutations lie in the dsdC region, are cis and trans recessive to dsdC+, and give rise to revertants of novel regulatory phenotype. The second class consists of Dsdase-negative lysogens in which the phenotype is the result of the integration of lambdac1857 Sam7 into the dsdC region. Lambda lysates derived from two of the Dsdase-negative lysogens can transduce the structural gene for Dsdase (dsdA) but not the dsdC region. The dsdC+ gene product had no repressor effect on constitutive synthesis in a strain containing a dsdO (initiator constitutive) and a dsdC- mutation. These and other findings indicate that control of Dsdase synthesis is strictly positive. The partial trans effect of the dsdC+ gene product on constitutive synthesis in dsdCc (regulator constitutive) strains can thus be explained by "subunit mixing" between active dsdCc subunits and dsdC+ subunits which are inactive in the absence of the inducer, D-serine. The order of genes in the dsd region is supN-dsdC-dsdP-dsdA-aroC.
mesh_terms: D002874:Chromosome Mapping; D003090:Coliphages / Q000254:growth & development; D004790:Enzyme Induction; D004794:Enzyme Repression; D004926:Escherichia coli / Q000201:enzymology* / Q000302:isolation & purification / Q000378:metabolism; D005796:Genes; D005808:Genes, Recessive; D005809:Genes, Regulator; D008040:Genetic Linkage; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D012695:L-Serine Dehydratase / Q000096:biosynthesis*; D008242:Lysogeny; D009153:Mutagens; D009154:Mutation; D009604:Nitrosoguanidines; D010641:Phenotype; D012694:Serine / Q000378:metabolism; D013237:Stereoisomerism; D013696:Temperature; D014161:Transduction, Genetic; D014779:Virus Replication
chemical_list: D009153:Mutagens; D009604:Nitrosoguanidines; D012694:Serine; D012695:L-Serine Dehydratase; D005947:Glucose; D005990:Glycerol