PerspectiveCell Biology

Fishing in the Nuclear Pore

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Science  01 Jul 2011:
Vol. 333, Issue 6038, pp. 44-45
DOI: 10.1126/science.1208568

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Cellular materials pass into and out of the nucleus of a eukaryotic cell through pores in the nuclear membrane. Each nuclear pore is a complex of ∼400 modular polypeptide chains [nucleoporins (Nups)] that form a cylindrical structure (1). The pore functions as a semipermeable filter that allows free diffusion of ions, small molecules, and macromolecules <40 kD in mass. Larger, soluble macromolecules that bear a nuclear localization signal (NLS) are ushered through by transport factors (2), but the molecular details of the mechanism remain mysterious. Even more perplexing is how membrane proteins transit from the outer to the inner nuclear membrane. Early models proposed either free diffusion and nuclear retention (3) or energy-dependent transport (4), whereas later results unexpectedly showed that the NLS-dependent transport mechanism for soluble proteins played a role (5). On page 90 of this issue, Meinema et al. (6) demonstrate an unprecedented mechanism for the latter model, showing that passage through the pore relies on the energetically unhindered, dynamic features of an intrinsically disordered (ID) domain in the membrane protein and the structural modularity and plasticity of the nuclear pore complex (NPC).