In vitro properties of RpoS (σs) mutants of Escherichia coli with postulated N-terminal subregion 1.1 or C-terminal region 4 deleted

Abstract

Derivatives of the stationary-phase sigma factor σs of Escherichia coli lacking either of two conserved domains, the postulated N-terminal subregion 1.1 or the C-terminal region 4, were shown to be competent in vitro for transcription initiation from several σs-dependent promoters on supercoiled DNA templates. Unlike wild-type σs, however, the deletion derivatives were inactive on relaxed templates. The anomalous slow electrophoretic mobility of σs on denaturing gels was corrected by deletion of subregion 1.1, suggesting that this domain in σs may be structurally and functionally analogous to subregion 1.1 of σ70, substitutions in which have previously been shown to rectify the anomalous electrophoretic migration of σ70 (V. Gopal and D. Chatterji, Eur. J. Biochem. 244:614-618, 1997).