Figure 7.

Degradation of FD transit peptide subfragment in the chloroplast depends on metal ions and ATP. Degradation assays with chloroplast extract were carried out using [³⁵S]methionine-labeled subfragment as substrate and analyzed by tricine SDS-PAGE for quantification. a, Reactivation of degradation activity by Zn²⁺ in the presence of 1,10-phenanthroline. Percent of subfragment remaining upon 30 min incubation in chloroplast extract without inhibitor and with 5 mM 1,10-phenanthroline at different Zn²⁺ concentrations. b, Reactivation of degradation activity by ATP after apyrase preincubation causes a loss of subfragment. Percent subfragment remaining after 30 min incubation in pretreated chloroplast extract without ATP or at 20 mM ATP. Chloroplast extract was preincubated with apyrase inactivated by boiling (inact.) or with different concentrations of active apyrase for 1 h at 37°C.