Ian Collinson
University of Bristol, United Kingdom

This paper is interesting because it reports a novel method for the regulation of an ATPase required to drive polypeptides through the bacterial inner membrane via the transmembrane protein-conducting channel SecYEG. Protein translocation through the SecY / Sec61 complex is an essential and conserved reaction and in bacteria it proceeds by the action of an ATP-driven protein pump associated with the protein conduction channel. The work identifies a conserved salt bridge or 'gate' in SecA that may form a switch to control different conformations in the nucleotide binding fold. As such, it may play an important role in relaying the conformational changes associated with ATP binding and hydrolysis to a power stroke responsible for the directional movement of polypeptides.