CRYSTALLOGRAPHIC STUDIES OF LARGE MACROMOLECULAR ASSEMBLIES

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。正在进行的项目包括参与基因表达所有步骤的大分子组装。其中第一个是复制体的组成部分，涉及复制DNA，包括复制DNA聚合酶III，DnaB解旋酶和引物酶。还在研究与钳复合并结合到DNA底物的钳装载器的结构。正在研究的第二个装配是核糖体，特别是50 S核糖体亚基，将被扩展到包括蛋白质合成过程中各种状态的整个70 S核糖体。用EF-Tu或EF-G或释放因子使70 S核糖体结晶的尝试正在进行中。此外，对70 S核糖体通过转座子分泌蛋白质的研究也沿着进行。第三个与基因表达无关的组装体是脂肪酸合成酶，它是一个分子量为250万的组装体，含有8种酶活性，其晶体在24 ID处的分辨率为3.8 <$D。为了理解多亚基酶的转录起始，人们正在研究与启动子DNA或6S RNA结合的大肠杆菌RNA聚合酶全酶。

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. The projects being pursued include large macromolecular assemblies that are involved in all steps of gene expression. The first of these are components of the replisome involved in copying DNA, including the replicating DNA polymerase III, DnaB helicase and primase. Also being pursued is the structure of the clamp loader complexed with the clamp and bound to a DNA substrate. The second assembly under study is the ribosome, specifically the 50S ribosomal subunit, is to be extended to include the entire 70S ribosome in various states of the protein synthesis process. Attempts to crystalize the 70S ribosome with EF-Tu, or EF-G, or release factors are underway. Further, studies of the translating 70S ribosome in the process of secreting protein through a translocon are well along. A third assembly not related to gene expression is that of fatty acid synthetase, a 2.5 million molecular weight assembly containing 8 enzyme activities, whose crystals diffract to 3.8 ¿ resolution at 24 ID. Finally, structural studies of the E. coli RNA polymerase holoenzyme bound either to a promoter DNA or 6S RNA are being pursued to understand transcription initiation in a multisubunit enzyme.