In Vitro Properties of RpoS (σ S ) Mutants of Escherichia coli with Postulated N-Terminal Subregion 1.1 or C-Terminal Region 4 Deleted

Abstract

ABSTRACT Derivatives of the stationary-phase sigma factor σ S 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 σ S -dependent promoters on supercoiled DNA templates. Unlike wild-type σ S , however, the deletion derivatives were inactive on relaxed templates. The anomalous slow electrophoretic mobility of σ S on denaturing gels was corrected by deletion of subregion 1.1, suggesting that this domain in σ S may be structurally and functionally analogous to subregion 1.1 of σ 70 , substitutions in which have previously been shown to rectify the anomalous electrophoretic migration of σ 70 (V. Gopal and D. Chatterji, Eur. J. Biochem. 244:614-618, 1997).