PHYSIOLOGICAL STUDIES OF SALMONELLA HISTIDINE OPERATOR-PROMOTER MUTANTS

[摘要] S. typhimurium hisO mutations are cis dominant and trans recessive and occur in a regulatory segment separate from but adjacent to the first structural gene of the histidine operon, hisG . Strains containing hisO mutations singly and in combination with other regulatory mutations were examined for their content of L-histidinol phosphate phosphatase when grown on limiting and on excess L-histidine. HisO mutations classed as "constitutive" (high enzyme levels) or as "promoter-like" (low enzyme levels) cause a variety of sub-phenotypes. A model is proposed that accounts for the phenotypes found as well as for the interspersion of constitutive and promoter-like mutations on the genetic map (Ely, Fankhauser and Hartman 1974). In this model we suggest that the his operator-promoter DNA is a functional unit that assumes alternate conformations including: (a) the classic linear duplex, active in transcription, and (b) a looped structure that is transcriptionally closed and susceptible to the binding of repressor.

[学科分类] 医学（综合）