Figure 2.

Transit peptides are converted to subfragments by SPP. Time courses of processing by immobilized SPP were carried out using [³⁵S]methionine-labeled precursors as substrates. Separation of precursor (P) and products (mature protein, M; transit peptide, T; subfragment of transit peptide, SF) was done by tricine SDS-PAGE, if not otherwise noted. PreFD alone (a) and with 5 mM 1,10-phenanthroline added after 2 min (b). PreHSP21 without (c) and with 5 mM 1,10-phenanthroline added after 5 min (d). PreLHCP wild-type (e) and mutant (f). The 90-min incubation was done in a separate experiment (e and f, lane 8). PreRBCA (g), the top shows a standard SDS-PAGE used to monitor generation of mature RBCA, the middle shows generation of T and SF₁, and the bottom shows an enlargement of lanes 2–5 of the middle panel. PreRBCA (h), to detect SF₂, the time for tricine SDS-PAGE was reduced. Autoradiograms with different exposure times were used for presentation of the top and the bottom part of a gel, as indicated by brackets at right.