The pore slides open

Structures of a nuclear pore protein, presented by Ivo Melčák, André Hoelz, and Günter Blobel (Rockefeller University, New York, NY), suggest that the pore's central channel expands by an unusual sliding between hydrophilic residues.

The crystals reveal structures of one of the four nucleoporins that make up the main channel. The authors suggest that the pore is encircled by eight side-by-side tetramers of this nucleoporin, called Nup58/45. The tetramer came in two forms; in one, the dimer–dimer interface was laterally displaced by ∼6 Å compared with the other.

Most protein interfaces depend on hydrophobic residues. But in Nup58/45, an electrostatic dimer–dimer interface permits expansion by allowing alternative hydrogen bond pairings. Hoelz describes this interaction as “the opposite of a...