FIGURE 6.

Scheme of SRP-mediated protein targeting. FtsY (green) is shown with the A domain (black) and the MTS (red). Prior to membrane interaction, the MTS is dynamic (red line) and undergoes a random coil-helix (red helix) transition upon interaction with anionic phospholipids, which are enriched at the SecYEG translocation channel (Step 1). This conformational switch allows subsequent interaction of FtsY with the RNC-SRP in a GTP-dependent manner (Step 2). Upon SRP-FtsY interaction, the two GTPases present in both proteins are activated (Step 3), and the cargo protein is inserted into the membrane (Step 4). GTP is indicated by T.