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

能力转录因子ComK与其调节因子Med之间的相互作用分析

基本信息

批准号：
10660099
负责人：
OGURA Mitsuo
金额：
$ 2.3万
依托单位：
Tokai University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

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.

枯草芽孢杆菌能力的主调节因子 ComK 是晚期能力操纵子转录所必需的。 ComK 在与 MecA 和 ClpC 形成的复合物中不活跃，但在 ComS 的作用下从复合物中释放后被激活。Med 已被发现是 MecA 下游 comK 功能的正调节剂。它是一种具有脂质修饰信号的假定脂蛋白。碱性磷酸酶与 Med 和 Western 分析的融合显示 Med 位于细胞膜的外表面。Western 和 Northern 分析显示 med 突变体中 ComK 减少。未磷酸化的 DegU 是调节外切蛋白酶产生的 DegS-DegU 双组分系统的响应调节因子，是 comK 转录所必需的，而磷酸化的 DegU 是外切蛋白酶产生所必需的。 degS 的缺失抑制了 med 突变的作用，表明 Med 可以调节 DegU 磷酸化，即抑制 DegU 磷酸化的因子可能通过 Med 依赖性方式掺入。我们发现多拷贝 phrG 抑制 aprE-lacZ 的表达并导致 comK 转录增加。向培养物中添加合成的 PhrG 五肽可减少 aprE-lacZ 的表达。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响应调节器 ComA 的激活，触发 comS 的转录。除了 RapC-PhrC 之外，RapG-PhrG 也被确定为 ComA 控制基因表达的调控系统。