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

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 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).