Figure 4.
Signal sequences from different substrates vary in their TRAP dependence. (A) Constructs containing the signal sequences of various mammalian proteins fused to PrP (Kim et al., 2002) were tested for their translocation into Q-depleted proteoliposomes lacking or containing RAMP-purified TRAP (as in Fig. 3 A). To facilitate direct comparisons, all constructs were analyzed in parallel using the same batch of proteoliposomes.The percent increase in overall translocation into the TRAP-containing proteoliposomes, relative to the membranes lacking TRAP, is plotted. The maximal overall translocation efficiency for each substrate (as a percent of total synthesized translation product) into proteoliposomes containing TRAP is indicated below the graph. The sequences and properties of the signals used in this experiment are depicted in Fig. 5. (B) The indicated signal sequences fused to the mature domain of bovine Prl were analyzed for their degree of dependence on TRAP for translocation, as in A.