Fig. 2. Activity of purified yeast SRP. (A) Confirmation of translocated species by protease protection. Translation reactions were carried out with or without addition of microsomal membranes (yRM) and subsequently incubated with 0.5 mg/ml proteinase K where indicated. (B and C) Translation reactions were carried out using extract containing (+) or immunodepleted of (–) SRP. yRM and purified SRP were added as indicated (concentrations of SRP in nanomoles). SRP was wild type except in (B) lane 13 and (C) lane 9, where SRP ΔC29 was used. (D) Translation reactions contained non-depleted extract supplemented with yRM and SRP (100 nM) as indicated. Reactions were run on 15% SDS–polyacrylamide gels and visualized by autoradiography. Untranslocated (ppL, ppαF and DHCαF) and processed, translocated (pL, gpαF and gDHCαF) species are indicated. Graphs were plotted using averaged data from three independent experiments. The translocation with non-depleted extract was set as 100%, bars, 1 SD.