Structure and function of the repressor of bacteriophage lambda |
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Authors: | D K Nag D J Chattopadhyay and N C Mandal |
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Affiliation: | (1) Department of Biochemistry, Bose Institute, 700 009 Calcutta, India;(2) Present address: Department of Microbiology and Immunology, Washington University School of Medicine, 63110 St. Louis, Missouri, USA;(3) Present address: Department of Biochemistry, University College of Science, 35, Ballygunj Circular Road, 700 019 Calcutta, India |
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Abstract: | Summary By mutagenizing a cIts (cI857) lysogen, a 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 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 plates on the lysogen of mutant 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 cIha (ha=high affinity). |
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