Fig. 9. Binding and insertion of TGD1 to isolated pea chloroplastic membranes. (A) TGD1; (B) the small subunit of rubisco, a typical stroma protein. ³⁵S-labeled TGD1 or the precursor of the rubisco small subunit (pSS) was bound to pea chloroplasts under low ATP conditions or imported under high ATP conditions for 30 min at room temperature. After binding or import, chloroplasts were incubated with (+TL) or without (–TL) thermolysin for 30 min at 4°C. Chloroplasts were recovered by centrifugation through a 40% Percoll cushion and fractionated into a total membrane (P) and soluble (S) fraction. All fractions were isolated and analyzed by SDS–PAGE and fluorography. TP represents 10% of translated product added to a single import assay; mSS, mature form of rubisco small subunit.