LAMBDA PHAGE MUTANTS INSENSITIVE TO TEMPERATURE-SENSITIVE REPRESSOR

Amino acid changes in the repressor of bacteriophage lambda due to temperature-sensitive mutations in its cI gene and the structure of a highly temperature-sensitive mutant repressor.

The mutant cIts genes from seven different lambdacIts phages carrying tsU50, tsU9, tsU46, ts1, tsU51, tsI-22 and ts2 mutations were cloned in plasmid. The positions of these mutations and the resulting changes of amino acids in the repressor were determined by DNA sequencing. The first four mutations mapping in the N-terminal domain show the following changes: I21S, G53S, A62T and V73A, respect...

Method for isolating restriction- and modificationless mutants of Escherichia coli K-12.

A simple method is described for the selection and isolation of restriction- and modificationless mutants in Escherichia coli K-12 by using the following properties: (i) the temperature-sensitive repressor activity of phage lambdacI857; (ii) a mutant of lambda phage defective in integration and the establishment of repression (lambdab2cI); (iii) a virulent lambda phage insensitive to the repres...

"Cold-sensitive" mutants of the Lac repressor.

Thirteen of more than 4,000 single-amino-acid-replacement mutants of the Lac repressor, generated by suppression of amber nonsense mutants, were characterized as having a cold-sensitive phenotype. However, when expressed as missense mutations, none of the replacements cause cold sensitivity, implicating the suppression mechanism as being responsible for this phenotype.

C-terminal deletions can suppress temperature-sensitive mutations and change dominance in the phage Mu repressor.

Mutations in an N-terminal 70-amino acid domain of bacteriophage Mu's repressor cause temperature-sensitive DNA-binding activity. Surprisingly, amber mutations can conditionally correct the heat-sensitive defect in three mutant forms of the repressor gene, cts25 (D43-G), cts62 (R47-Q) and cts71 (M28-I), and in the appropriate bacterial host produce a heat-stable Sts phenotype (for survival of t...

Successful expression of a selenomethionyl protein under control of the temperature-sensitive lambda repressor requires higher than normal temperature.