Protein translocation pulls the plug

Membrane-bound compartments present an immediate problem: proteins need to get into and across those membranes. Now, we have the first picture of how that process works, thanks to the structure determined by Bert van den Berg, William Clemons, Jr., Stephen Harrison, Tom Rapoport (Harvard Medical School, Boston, MA), and colleagues. They find that a single SecY complex from Methanococcus jannaschii forms an hourglass-shaped pore with a basal plug that probably swings out of the way to let nascent protein chains pass.

The complex was not an easy target: the structure came only after five years of experiments with proteins from ten different organisms. The effort was worthwhile. “In contrast to ion channels and other structures … where people had models before the structure was solved, in this case we really didn't have any ideas...