Figure 1.

A three dimensional model of the nuclear pore. This stunning model of the nuclear pore machine is based on images from electron and atomic force microscopes and sumarises the current state of knowledge of the structure of the nuclear pore. Transport of macromolecules into the nucleus occurs from the top to the bottom of the model. Cytoplasmic fibrils (top, blue) extend from the surface of the pore into the cytoplasm and are thought to function as tracks that guide macromolecular complexes destined for the nucleus to the pore opening. The pore itself is a symmetrical ring (pink) that perforates the double bilayer nuclear membrane (light blue). The ellipsoidal material (transparent blue) in the centre of the pore represents the plug often seen in images of pores. Finally, the nucleoplasmic basket (red) may open and close to regulate the import and export of material. Figure kindly provided by Daniel Stoffler (University of Basel).