A Modular Model of the Nuclear Pore Complex
The nuclear pore complex (NPC) is a singular assembly which spans the double membrane of the nuclear envelope and mediates nucleocytoplasmic transport (for a review see Newport & Forbes, 1987). In order to understand these transport processes, I am currently devising methods to solve the 3-dimensional structures of various NPCs, including forms with a dilated central channel (transporter). The first step in this process is determining the 2-dimensional structures and possible interrelationships of the different classes of NPCs observed in isolated amphibian nuclear envelopes. Cryo-electron microscopy of frozen-hydrated specimens, coupled with image analysis of a 4700 particle globally aligned database, has allowed verification of the NPC model proposed by Unwin & Milligan (1982). The model has been extended to 50-60 angstrom resolution and new features relevant to the in vivo function of the assembly have been observed. Significantly, projected structures of the NPC-transporter in different transport-related states have been obtained and an initial model is proposed.
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