Hydrogel Could Sort Out Cellular Traffic

A surprisingly simple hydrogel made from amino acid repeat units mimics the exquisite selectivity of the giant protein pores that control traffic between the nucleus and cytoplasm and may shed light on how these pores do their job (Cell 2007, 130, 512). So-called nuclear pore complexes (NPCs) block the passage of anything larger than 30 kDa, unless the cargo is strapped to an appropriate transporter protein. But NPCs' large size has made them difficult to study structurally, so the molecular details of the pores' remarkable selectivity have remained unclear. Steffen Frey and Dirk Görlich of the Max Planck Institute for Biophysical Chemistry, Göttingen, Germany, designed and constructed a sievelike protein hydrogel from pieces of the phenylalanine- and glycine-rich protein domains thought to crowd the pores' center. Like NPCs, the hydrogel excludes molecules above 30 kDa but allows large transporter-bound cargoes to pass, presumably because the transporter binds and disrupts the hydrophobic clusters that tie the hydrogel together.