Fig. 5. Protein import into tom22-2 mitochondria. (A) Import of purified b₂Δ-DHFR into wild-type (WT) or tom22-2 mitochondria (80 mM KCl in import buffer). Where indicated, the mitochondria were treated with proteinase K after the import reaction. The mitochondria were reisolated and analyzed by SDS–PAGE. The amount of processed (i-form) of b₂Δ-DHFR in energized wild-type mitochondria after a 16 min import was set to 100% (control). (B) Import of purified b₂Δ-DHFR in the presence of 250 mM KCl. The experiment was performed as described for (A). (C) Dependence of b₂Δ-DHFR import on the ionic strength. The experiment was performed as described above at the indicated concentrations of KCl. The ratio of imported protein in tom22-2 mitochondria to wild-type mitochondria is shown.