DYNAMICS AND FUNCTIONAL MOTIONS OF THE GLPG INTRAMEMBRANE PROTEASE

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 膜内蛋白水解酶是一种膜内蛋白水解酶，它能裂解跨膜底物，释放参与重要细胞过程的分子，如细胞信号传递。大肠杆菌产生的GlpG膜内酶是目前研究最多的膜内酶之一。为了与底物对接，GlpG必须朝向脂质双层开放才能接纳底物。由蛋白酶的第五个螺旋形成的侧门显然控制着进入；靠近活性部位的环的运动，被称为帽环，也可能有助于底物对接。一个有趣但鲜为人知的实验观察结果是，脂质双层的组成极大地影响了GlpG的催化活性：例如，磷脂酰乙醇胺脂头基团，而不是磷脂酰胆碱，与催化底物切割相容(Urban&Wolfe，2005)。 我们在&lt；100 ns时间尺度上的分子动力学模拟表明，蛋白酶的几个环，包括帽环，经历了不同的构象转变，这取决于周围的脂类头基(Bondar等人，2009；Bondar&White，工作中)。例如，在由1-palmytoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine(POPC)组成的脂质双层中，环的构象转变发生在30 ns内，并且几乎同时发生，而在1-palmytoyl-2-oleoyl-sn-glycero-3-phosphatidylethanolamine(POPE)中，构象转变在时间上明显分离，需要长达80 ns。由于我们模拟的时间尺度有限，我们不能排除我们观察到的构象转变是可逆的，或者在更长的时间尺度上可能发生进一步的构象变化(例如，侧门的打开)。Anton实现的微秒级模拟对于采样和表征GlpG作为膜内酶模型系统的脂类依赖的构象转变将是非常宝贵的。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Intramembrane proteases are membrane-embedded proteases that cleave transmembrane (TM) substrates to liberate molecules that participate in important cellular processes, such as cell signaling. The GlpG intramembrane protease from E. coli is one of the best studied intramemembrane proteases. To dock its substrate, GlpG must open towards the lipid bilayer to admit the substrate. A lateral gate formed by the fifth helix of the protease apparently controls admission; motions of a loop near to the active site, denoted as the cap loop, may also assist substrate docking. An intriguing and little understood observation from experiments is that the composition of the lipid bilayer affects drastically the catalytic activity of GlpG: for example, phosphatidylethanolamine lipid headgroups, but not phosphatidylcholine, are compatible with catalytic substrate cleavage (Urban & Wolfe, 2005). Our molecular dynamics simulations on the <100ns timescale demonstrated that several loops of the protease, including the cap loop, undergo distinct conformational transitions that depend on the surrounding lipid headgroups (Bondar et al, 2009; Bondar & White, work in progress). For example, in a lipid bilayer composed of 1-palmytoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) the conformational transitions of the loops occur within 30ns and are almost simultaneous, whereas in 1-palmytoyl-2-oleoyl-sn-glycero-3-phosphatidylethanolamine (POPE) the conformational transitions are clearly separated in time, and require up to 80ns. Due to the limited timescale of our simulations, we cannot exclude the possibility that the conformational transitions we observe are reversible, or that further conformational changes (e.g., opening of the lateral gate) could occur on the longer timescale. The microsecond-timescale simulations made possible by Anton will be invaluable for sampling and characterizing the lipid-dependent conformational transitions of GlpG as model system for intramembrane proteases in general.