Figure 5.

The Twin-Positive Motif Is Necessary for Efficient Import of prcpHsc70-1 into Leucoplasts.

(A) Transit-peptide sequences of prcpHsc70-1 and the K23R24→AA mutant. The twin-positive motif at positions 23 and 24 is denoted in boldface letters and underlined. The Ala residues replacing the twin-positive motif are colored red.

(B) and (C) Import of [³⁵S]Met-prcpHsc70-1 and the K23R24→AA mutant into leucoplasts (B) and chloroplasts (C), respectively. [³⁵S]Met preproteins were incubated with isolated leucoplasts (Leu) or chloroplasts (Cpt) under import conditions for 10 min. Intact plastids were reisolated and analyzed by SDS-PAGE. The import efficiency of each preprotein was calculated. Data shown are means ± sd of four independent experiments. Tr, 12.5 and 25% input for leucoplast (B) or chloroplast (C) experiments, respectively. pr and m indicate precursor and mature forms, respectively.