A carboxy-terminal 16-amino-acid region of sigma(38) of Escherichia coli is important for transcription under high-salt conditions and sigma activities in vivo

sigma(38) (or sigma(s), the rpoS gene product) is a sigma subunit of RNA po lymerase in Escherichia coli and directs transcription from a number of sta tionary-phase promoters as well as osmotically inducible promoters. In this study, we analyzed the function of the carboxy-terminal 16-amino-acid regi on of sigma(38) (residues 315 to 330), which is well conserved among the rp oS gene products of enteric bacterial species. Truncation of this region wa s shown to result in the loss of sigma activity in vivo using promoter-lacZ fusion constructs, but the mutant sigma(38) retained the binding activity in vivo to the core enzyme. The in vitro transcription analysis revealed th at the transcription activity of sigma(38) holoenzyme under high potassium glutamate concentrations was significantly decreased by the truncation of t he carboxy-terminal tail element.