Fig. 3. Insertion of Toc34 into protein-free membranes depends on the transmembrane region. (A) [³H]-Leucine-labelled Toc34 (lane 1) was treated with thermolysin (Thr, lanes 2, 4 and 6) before (lane 2) and after insertion into free liposomes (1 mM final lipid concentration, lanes 3-6), followed by incubation in 100 mM Na₂CO₃ (lanes 5 and 6) for 30 minutes at 4°C and pelleting of the membrane fraction. (B) [³H]-Leucine-labelled Toc34-252 and [³⁵S]-methionine-labelled Tic40 (10% TP, lane 1) were incubated with liposomes (lanes 2-4) without (lane 2) and with (lanes 3, 4) competition with N-liposomes, followed by thermolysin treatment (lane 4).