BIOPHYSICS: Exposing the Innards

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Science  30 Aug 2002:
Vol. 297, Issue 5586, pp. 1449c
DOI: 10.1126/science.297.5586.1449c

The quantitative analysis of how molecules cross biological membranes has relied on in vitro preparations in which the solute compositions on both sides of the membrane are accessible to the experimenter; for instance, both right-side-out and inside-out erythrocyte ghosts have been used to measure anion flux. Making such measurements across internal membranes has been especially daunting, but Siebrasse and Peters describe a method for monitoring passage through nuclear pore complexes (NPCs), large channels about 10 nm in diameter that allow movement of macromolecules between the cytoplasm and the nucleus. They show that NTF2, a protein that binds to the FG repeats of the nucleoporin components of the NPC, is transported about 50 times faster than an inert comparably sized protein, with a turnover rate of 100 molecules s−1 NPC−1. Also in this system, Siebrasse et al. have been able to reconstitute nuclear transport that is dependent on both an export receptor and the GTP-binding protein Ran. — GJC

EMBO Rep. 10.1093/embo-reports/kvf171 (2002); J. Cell. Biol., in press.

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