CRYSTAL STRUCTURES OF SECA AND SECT-SECYEG COMPLEXES

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 1.许多蛋白质在合成后通过细菌质膜转运。它们由SecA ATPase通过一个由异源三聚体膜蛋白复合体形成的易位通道移动，称为SecYEG复合体。以前已经确定了SecA ATPase的结构，也确定了来自考古菌的通道结构。因此，下一步是确定与通道结合的SecA ATPase的结构。 2.SecA是一种ATPase，负责细菌中多肽通过SecY通道的翻译后移位。已经确定了几种SECA结构，但对ATPase的功能还没有完全的了解。一个主要问题与赛卡二聚体的作用有关。我们已经获得了数据，表明SecA作为单体发挥功能，而其他人则声称它作为二聚体发挥功能。除了解决这个问题，我们开始对Thermotoga maritima Seca的结构感兴趣，因为我们已经将该物种的SecA结晶在与通道的络合物中(见上文)。问题是Maritima Seca在与通道结合后是否会发生构象变化。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. 1. Many proteins are transported after their synthesis across the bacterial plasma membrane. They are moved by the SecA ATPase through a translocation channel that is formed by a heterotrimeric membrane protein complex, called the SecYEG complex. Structures of the SecA ATPase had been determined before and a structure of the channel from an archaebacterium had also been determined. The next step was therefore to determine the structure of the SecA ATPase bound to the channel. 2. SecA is the ATPase that is responsible for the post-translational translocation of polypeptides across the SecY channel in bacteria. Several SecA structures have been determined, but a full understanding of the function of the ATPase has not yet been achieved. One major question concerns the role of a SecA dimer. We had obtained data that suggested that SecA functions as a monomer, while others have claimed that it functions as a dimer. In addition to resolving this issue, we became interested in the structure of Thermotoga maritima SecA because we had crystallized the SecA from this species in complex with the channel (see above). The question was whether T. maritima SecA undergoes conformational changes upon binding to the channel.