Elucidating the molecular details of RssB-mediated turnover of SigmaS by the AAA+ protease, ClpXP and its inhibition by anti-adaptors. (#153)
The general stress response provides a pathway for bacteria to survive in response to a range of different environmental stresses. This pathway is largely controlled at the post-translational level through the regulated degradation of the transcription factor, SigmaS (σS). Under normal conditions, the phosphorylated adaptor protein RssB recognises σS and delivers it to the ClpXP protease where it is rapidly degraded. In contrast, under conditions of “general” stress the turnover of σS is inhibited by a number of stress-specific anti-adaptors, which as the name suggests inhibit the activity of the adaptor protein, RssB. Currently however, the molecular details of the steps which lead to, or prevent, σS turnover are poorly defined. Here we describe our current understanding of the molecular details of this process. Using a range of biochemical assays we have identified not only the mechanism by which σS is recognised by RssB and delivered to ClpXP for degradation, but also the molecular details of the interaction between RssB and the various anti-adaptor proteins, which prevent its delivery. Collectively, these data improve our understanding of σS turnover and the general stress response.