Figure 4.

SRP is also required for the membrane integration of SecY. SecY was synthesized using plasmid pJM8CS7, encoding secY under the T7 promotor, in the presence of the components indicated (for experimental details see legends of Figures 2 and 3). Membrane integration of newly synthesized SecY was analyzed by subfractionation of the translation products on a two-step sucrose gradient (see MATERIALS AND METHODS for details). Radioactivity present in the individual SecY bands was quantitated and the sum of the three subfractions was set at 100%.