Cell Biology

Nuclear Pore Mapped

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Science  17 Mar 2000:
Vol. 287, Issue 5460, pp. 1889
DOI: 10.1126/science.287.5460.1889b

The nucleus of eukaryotic cells is surrounded by a double membrane punctuated by pores through which proteins and RNAs travel. Rout et al. have conducted a systematic proteomics study of the yeast nuclear pore complex: separating protein components by chromatography and electrophoresis; identifying molecules by peptide sequencing and mass spectrometry; and localizing them by subcellular fractionation and immunofluorescence.

The pore complex is composed of approximately 30 different proteins, which are assembled in a repeated motif to form two stacked rings. Filaments (FG Nups—nucleoporin proteins containing the phe-gly motif) extend from the pore complex towards the cytosol where they are thought to usher incoming nuclear proteins into the pore. On the nucleoplasmic side of the pore, similar filaments form a basket-like structure through which imported proteins enter the nucleus. The structure is remarkably symmetrical, given the vectorial nature of traffic across the pore. The authors suggest that the pore mediates transport by providing multiple high-affinity binding sites for karyopherins (Kap) on one side, which promote diffusion through the pore, after which the high-affinity interactions are inactivated and the cargo macromolecules released.—SMH

J. Cell Biol.148, 635 (2000).

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