CORE ASSEMBLY OF THE NUCLEAR PORE COMPLEX

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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 nuclear envelope is a double-layered membrane that separates the nucleus from the cytoplasm in the eukaryotic cell. The NE is perforated by nuclear pore complexes (NPCs) which constitute the only gateway into and out of the nucleus. The NPC is a very large protein assembly composed of several hundred polypeptides and an estimated mass of 60-80 MDa. As a whole, the NPC is currently not amenable to X-ray crystallographic analysis since it cannot be produced in large enough and pure quantities. In our approach, we exploit the fact that the NPC is a highly modular structure. The modularity is reflected in four layers: 1) the NPC has an eight-fold rotational symmetry; 2) it is composed of a limited set of about 30 proteins, called nucleoporins or nups, that occur in multiples of eight; 3) Nups are organized in discrete subcomplexes that are biochemically defined; 4) Individual nups are largely composed of a small number of structural domains. Exploiting this high level of modularity we are working on the elucidation of those subcomplexes that make up the core scaffold of the NPC. We will combine high-resolution X-ray structures with electron-microscopic images to create composite models of substantially higher level of detail than currently available. Such models will provide a means to unravel the functional principles of the NPC on a molecular level.