Analysis of the Role of RsbV, RsbW, and RsbY in Regulating σB Activity in Bacillus cereus

摘要

The alternative sigma factor σB is an important regulator of the stress response of Bacillus cereus. Here, the role of the regulatory proteins RsbV, RsbW, and RsbY in regulating σB activity in B. cereus is analyzed. Functional characterization of RsbV and RsbW showed that they act as an anti-sigma factor antagonist and an anti-sigma factor, respectively. RsbW can also act as a kinase on RsbV. These data are in line with earlier functional characterizations of RsbV and RsbW homologs in B. subtilis. The rsbY gene is unique to B. cereus and its closest relatives and is predicted to encode a protein with an N-terminal CheY domain and a C-terminal PP2C domain. In an rsbY deletion mutant, the σB response upon stress exposure was almost completely abolished, but the response could be restored by complementation with full-length rsbY. Expression analysis showed that rsbY is transcribed from both a σA-dependent promoter and a σB-dependent promoter. The central role of RsbY in regulating the activity of σB indicates that in B. cereus, the σB activation pathway is markedly different from that in other gram-positive bacteria.