Construction of an Efficient In Vitro System for Analysis of Transcription from Sigma 54-Dependent pspA Promoter

摘要

IbsC is a small toxin protein in Escherichia coli, whose expression is repressed by a as-acting small noncoding RNA, SibC (renamed from RygC or QUADlc). Over-expression of IbsC or the absence of SibC transcription induces the expression of both psp operon (pspABCDE) and pspG gene encoding phage shock proteins, whose expression were known to be induced by multiple environment stresses or agents such as filamentous phage infection, osmotic shock, continued incubation in stationary phase, heat shock, and ethanol treatment. Although exogenous overexpression of IbsC leads to cell death, physiological roles of IbsC remain unknown especially because the strain without ibsC gene in the chromosome shows no growth defects. Considering that only Psp proteins are induced by expression of IbsC, not by other similar small toxin proteins such as LdrD, ShoB, and TisB, the role of IbsC might specifically be related to phage shock proteins.