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Science 3 November 2006:
Vol. 314. no. 5800, p. 721
DOI: 10.1126/science.314.5800.721h
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Nuclear pore complexes behave like a sieve--they allow small molecules to pass freely but restrict passage of macromolecules (>30 kilodaltons) between the nucleus and cytosol. The so-called FG-rich nucleoporin repeats, which are intrinsically unfolded protein domains that contain short clusters of hydrophobic amino acids separated by hydrophilic spacer regions, are thought to form the barrier, but the functional organization of this barrier has remained a matter of speculation. Frey et al. (p. 815; see the Perspective by Burke and the Perspective by Elbaum) show that these FG-rich repeats occur in an extended conformation and form a noncovalent (and thus reversible) hydrogel. Hydrophobic bridges connecting the individual polypeptide chains and create a three-dimensional sieve-like structure that is crucial for nuclear pore complex function.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)