A novel anti‐anti‐activator mechanism regulates expression of the Pseudomonas aeruginosa type III secretion system

摘要: Summary Expression of the Pseudomonas aeruginosa type III secretion system (TTSS) is coupled to status cells. Environmental signals such as calcium depletion activate channel and, a consequence, gene transcription derepressed. Two proteins, ExsA and ExsD, were shown previously play role in coupling secretion. an activator TTSS transcription, ExsD anti-activator ExsA. In absence environmental cues, binds inhibits transcription. Here, we describe characterization ExsC anti-anti-activator expression. Transcription repressed exsC mutant derepressed upon overexpression. The dependence on for relieved exsD, suggesting that function together regulate Consistent with this idea, interacts bacterial two-hybrid co-purification assays. We propose model which (ExsC) sequesters (ExsD) under low Ca2+ conditions, freeing allowing TTSS. P. represents first example anti-activator/anti-anti-activator pair controlling