Fig. 4. Toc75-V is not present in the isolated Toc complex. Purified outer envelope membranes from pea chloroplasts were solubilized in 1.5% decylmaltoside for 10 min at ambient temperature and fractionated at 200 000 g on a linear sucrose density gradient (25–70%, w/v). Lane 1 shows an immunoblot of total solubilized membranes using antisera against Toc159 (the presence of the preteolytic fragment of 86 kDa is shown), Toc75-III, Toc75-V, Tic40, Toc34 and the outer envelope protein OEP24. Lanes 2–7 show immunoblots of different fractions of the sucrose density gradient using the same antisera as in lane 1. The Toc complex consisting of the subunits Toc159, Toc75-III and Toc34 is concentrated in fraction 20, whereas Toc75-V did not enter the gradient.