Isolation and genetic characterization of the nitA mutants of Escherichia coli affecting the termination factor rho

Publisher Website
Google Scholar
Abstract
Taking advantage of the Spi (Sensitivity to P2 interference) phenomenon, bacterial mutants seemingly resistant to phage λsusN7nin5, but sensitive to phage λspi, were isolated from a strain of E. coli K12 carrying no nonsense suppressor and lysogenic for P2. A class of these mutants, designated nitA (N-independent transcription), is described here. Upon infection of the nitA mutants with a trp transducing phage λsusN7N53ptrp46 which carries the E. coli trpE and D genes in the CIII-att region of the λ genome, formation of anthranilate synthetase (ASase, a complex protein of trp E and D gene products) was clearly demonstrated. In contrast, no ASase formation was observed in the parent nitA +strain under the same conditions. The synthesis is subject to “turn off” control, and is completely repressed by the CI repressor of phage λ. The nitA cells lysogenic for λCI857susN7N53 are killed by thermal induction much more efficiently than the parent cells lysogenic for the same phage. The nitA mutants support the growth of λsusN7N53byp much better than the parent. These results suggest that the nitA mutation permits the early leftward and rightward transcription of the λ genome in the absence of the N gene product. On the E. coli genetic map, nitA is located between ilv and metE, nearer to ilv. The mutant allele is recessive to the wild-type allele. The present evidence, together with results of biochemical investigations to be reported, suggests that nitA is a gene specifying the transcription termination factor rho.

This publication has 51 references indexed in Scilit: