An adaptor protein network that controls general and regulated proteolysis in Bacillus subtilis

蛋白质质量控制系统对于确保细胞蛋白质稳态和监测所有细胞中蛋白质的折叠和活性状态至关重要。这些高度保守的系统包括分子伴侣系统，但也包括AAA+蛋白酶复合物，如细菌中的Hsp 100/Clp蛋白。通过分子伴侣拯救和修复功能蛋白和/或通过降解去除潜在毒性错误折叠蛋白种类的能力可以被认为是相同细胞蛋白质质量控制系统的两个分支。有趣的是，相同的AAA+蛋白酶系统通过例如转录因子的调节性蛋白水解同时参与细胞和发育过程的信号转导和控制。蛋白水解由专用分子机器介导，其通过与区室化桶样肽酶相关的六聚体AAA+马达蛋白成环而形成。这种蛋白水解复合物的实例是真核细胞中的蛋白酶体或与ClpP相互作用的原核Hsp 100/Clp蛋白。通常，相同的蛋白水解机器另外用于调节目的，例如像关键转录因子的调节蛋白水解以控制例如发育过程。我们感兴趣的是了解在原核细胞中，为了不同的调节或蛋白质质量控制原因，降解蛋白质的重要和最终细胞决定是如何做出的。土壤细菌枯草芽孢杆菌的ClpCP参与一般蛋白质质量控制和调节过程。我们可以证明，对于ClpCP，衔接蛋白如MecA、YpbH或McsB是激活ClpCP蛋白酶所必需的，并且对于底物识别和选择是重要的。根据我们最近的研究结果，我们建议更详细地解决这个系统的两个有趣的和新的方面。(1)我们希望调查和可能了解之间的相互作用的展开或重塑和蛋白水解模式的Hsp 100/Clp蛋白在体内和体外。(2)我们想研究衔接蛋白介导的ClpC激活的作用和功能，特别强调蛋白质精氨酸激酶McsB。我们将使用各种体内和体外实验来测试我们关于McsB在蛋白质解聚中的潜在作用的假设。

Protein quality control systems are essential to ensure cellular protein homeostasis and monitor the folding and active state of proteins in all cells. These highly conserved systems include chaperone systems but also AAA+ protease complexes such as Hsp100/Clp proteins in bacteria. The ability to rescue and repair functional proteins by chaperones and/or to remove potentially toxic misfolded protein species by degradation could be considered as two branches of the same cellular protein quality control system. Interestingly, the same AAA+ protease systems are concurrently involved in the signal transduction and control of cellular and developmental processes by regulatory proteolysis of e.g. transcription factors. Proteolysis is mediated by dedicated molecular machines, which are formed by ringforming hexameric AAA+ motor proteins, associated with compartmentalized barrel-like peptidases. Examples for such proteolytic complexes are the proteasome in eukaryotic cells or the prokaryotic Hsp100/Clp proteins interacting with ClpP. Often the same proteolytic machines are used in addition for regulatory purposes, e.g. like regulated proteolysis of key transcription factors to control for example developmental processes. We are interested to understand how in prokaryotic cells the important and terminal cellular decision to degrade a protein for distinct and different regulatory or protein quality control reasons is taken. ClpCP of the soil bacterium Bacillus subtilis is involved in general protein quality control and regulatory processes. We could demonstrate for ClpCP that adaptor proteins like MecA, YpbH or McsB are necessary to activate the ClpCP protease and important for substrate recognition and selection. Based on our recent results we propose to address two interesting and new aspects of this system in more detail. (1) We want to investigate and possibly understand the interplay between the unfolding or remodeling and proteolytic mode of the Hsp100/Clp proteins both in vivo and in vitro. (2) We want to investigate the role and function of the adaptor protein mediated ClpC activation with a special emphasis on the protein arginine kinase McsB. We will test our hypothesis concerning the potential role of McsB in protein disaggregation using various in vivo and in vitro experiments.