Activation without Proteolysis of Anti-iσ/iFactor RsiV of the Extracytoplasmic Function iσ/iFactor iσ/isupV/supin a Glucolipid-Deficient Mutant of iBacillus subtilis/i

摘要

Extracytoplasmic function (ECF) σ factors are a crucial link in the process of bacterial response to environmental stresses, in which bacteria transmit information across the cytoplasmic membrane. Among the seven ECF σ factors of Bacillus subtilis σV, which is sequestered by transmembrane anti-σ factor RsiV under normal growth conditions, responds to lysozyme. When B. subtilis cells are challenged by lysozyme, the lysozyme-bound RsiV undergoes two successive proteolysis steps, by a signal peptidase and RasP protease, and releases σV. An unchallenged B. subtilis ugtP mutant lacking glucolipids exhibited higher σV activity than wild type. However, the activation occurred in the absence of RasP, and no proteolysis of RsiV was observed. It is likely that a conformational change, not proteolysis, of RsiV leads to this activation of σV in the absence of glucolipids. Replacement of the C-terminal region of RsiV with that of RsiW, the cognate σ factor of which, σW, is not activated in the ugtP mutant, indicated that the C-terminal extracytoplasmic region of RsiV was necessary for the response to glucolipid deficiency.