Mapping out forces that act on transmembrane helices during membrane insertion

Membrane proteins destined for insertion into the inner membrane of E. coli are synthesized by ribosomes bound to the SecYEG translocon. During co‐translational membrane integration, transmembrane α‐helical segments in the nascent chain exit the translocon through a lateral gate that opens towards the surrounding membrane, but the mechanism of gate opening and lateral exit is not well understood. In particular, little is known about how a transmembrane helix behaves when inside the translocon. Current work in our lab has shown that a force proportional to the free energy of membrane insertion is exerted on a transmembrane helix when it transits through the translocon channel, providing a direct insight into the dynamics of membrane integration.