CRYSTALLOGRAPHIC STUDIES OF LARGE MACROMOLECULAR ASSEMBLIES

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。正在进行的项目包括涉及基因表达所有步骤的大型大分子组装。第一类是参与复制DNA的复制体的组成部分，包括复制DNA聚合酶III， DNA解旋酶和引物酶。还在研究夹钳装载器与夹钳络合并结合到DNA底物的结构。第二个正在研究的组装是核糖体，特别是50S核糖体亚基，将被扩展到包括整个70S核糖体在蛋白质合成过程的各种状态。正在尝试用EF-Tu或EF-G或释放因子结晶70S核糖体。此外，对翻译70S核糖体通过转座子分泌蛋白质过程的研究进展顺利。第三种与基因表达无关的组装是脂肪酸合成酶，这是一个250万分子量的组装，含有8种酶活性，其晶体在24 ID下衍射到3.8¿分辨率。最后，大肠杆菌RNA聚合酶全酶与启动子DNA或6S RNA结合的结构研究正在进行，以了解多亚基酶的转录起始。

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.