FIGURE 9.

The effect of urea on membrane association and transport of Plsp1. A, effects of post-transport treatment of urea on membrane-associated Plsp1. After the assay as described in Fig. 4A, the recovered chloroplast membranes were resuspended with buffer containing the indicated concentrations of urea and incubated at room temperature in the dark for 10 min. The membranes were recovered by centrifugation and treated with the same buffer again. The resultant membrane fractions were resuspended in import buffer and treated without (−) or with (+) thermolysin (t-lysin) before analysis as described in Fig. 2A. The degradation products of Plsp1 (dp1 and dp2) and precursor (pr), intermediate (i), mature (m), and degradation product (dp) of PsbW are indicated. B, effects of urea on SE-independent insertion of Plsp1 into isolated chloroplast membranes. Radiolabeled proteins indicated at left were incubated with isolated chloroplast membranes in the light in the absence of SE with the indicated concentrations of urea. The reactions were incubated and analyzed as described for Fig. 4.