title: Structure and function of the repressor of bacteriophage lambda. II. Isolation and characterization of a lambda mutant which produces repressor having higher affinity for operators.
abstract: By mutagenizing a lambda cIts (lambda cI857) lysogen, a lambda mutant has been isolated with a wild-type phenotype. This mutant phage lysogenizes with low efficiency and produces a low burst. Though the initial rates of repressor synthesis in Escherichia coli after infection with wild-type and mutant lambda are the same, the maximum level of repressor that is synthesized in the latter case is only about 30% of that synthesized in the former. Virulent lambda plates on the lysogen of mutant lambda with slightly less efficiency producing very tiny plaques. Operator-binding studies made in vitro with purified mutant and wild-type repressors show that the binding curve of the former repressor is a rectangular hyperbola while that of the latter is sigmoid. The half-lives of the complexes of mutant and wild-type repressors with right operator are 133 and 27 min, respectively. All these results suggest that the mutant repressor possibly has a higher affinity for the operators. This mutant has been named lambda cIha (ha = high affinity).
mesh_terms: D010582:Bacteriophage lambda / Q000235:genetics* / Q000254:growth & development; D004279:DNA, Viral / Q000378:metabolism; D004268:DNA-Binding Proteins; D008242:Lysogeny; D009876:Operon; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics*; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D004279:DNA, Viral; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins