FIGURE 3.

MBP^*1_SP-enzyme chimeras are recognized effectively by SRP. The N-terminal 86 residues of the indicated MBP_SP-enzyme or MBP^*1_SP-enzyme (including the signal peptide) were synthesized in coupled transcription-translation reactions. Portions of each reaction that were treated with the cross-linker BS³ (lanes 1–3, 7–9, and 13–15) or untreated (lanes 4–6, 10–12, and 16–18) were analyzed by SDS-PAGE. T, major translation products; X, ∼58-kDa cross-linked product; ^*, ∼60-kDa cross-linked product. Portions of each sample that were treated with the cross-linker were also subjected to immunoprecipitation with an anti-Ffh antiserum (lanes 19–27).