Analysis of interaction between the competence transcription factor, ComK and its regulatory factor, Med

B的主调节器。枯草芽孢杆菌感受态ComK是晚期感受态操纵子转录所必需的。ComK在与MecA和ClpC的复合物中是无活性的，但在通过ComS的作用从复合物释放时被激活。它是一种具有脂质修饰信号的推定脂蛋白。碱性磷酸酶与Med的融合和Western分析显示Med定位于细胞膜的外表面。Western和北方分析显示Med突变体中ComK减少。非磷酸化DegU是调节外切蛋白酶产生的DegS-DegU双组分系统的响应调节剂，对于comK的转录是必需的，而磷酸化DegU对于外切蛋白酶产生是必需的。med突变的作用被degS的缺失抑制，表明Med可以调节DegU磷酸化，即，抑制DegU磷酸化的因子可以通过Med依赖性方式掺入。我们已经发现，多拷贝phrG抑制aprE-lacZ的表达，并引起comK转录的增加。向培养物中添加合成的PhrG五肽降低了aprE-lacZ表达。这些结果表明，phrG可能通过DegU正向调节comK的转录，PhrC五肽的群体感应调节导致反应调节因子ComA的激活，从而触发comS的转录。RapG-PhrG也被确定为除了RapC-PhrC之外的ComA控制基因表达的调控系统。

A master regulator for B. subtilis competence, ComK, is required for transcription of late competence operons. ComK is inactive in a complex with MecA and ClpC, but is activated upon release from the complex by the action of ComS.Med has been found as a positive regulator for comK functioning downstream from MecA. It is a putative lipoprotein with a lipid modification signal. An alkaline phosphatase fusion with Med and Western analysis revealed localization of Med on the outer surface of the cell membrane.Western and Northern analyses showed a decrease of ComK in the med mutant. Unphosphorylated DegU, a response regulator of the DegS-DegU two-component system regulating exoprotease production, is necessary for transcription of comK, whereas phosphoryrlated DegU is necessary for exoprotease production. The effect of the med mutation was suppressed by deletion of degS, suggesting that Med could modulate DegU phosphorylation, I.e., a factor inhibiting DegU phosphorylation might be incorporated by a Med-dependent manner. We have found that multicopy phrG inhibited the expression of aprE-lacZ and caused an increase in comK transcription. Addition of a synthetic PhrG pentapeptide to the culture reduced aprE-lacZ expression. These results suggested that phrG positively regulates transcription of comK possibly through DegU.Quorum sensing regulation by the PhrC pentapeptide results in activation of a response regulator, ComA, triggering transcription of comS. RapG-PhrG was also identified as the regulatory system for expression of the ComA-controlled genes in addition to RapC-PhrC.