Figure 4.

SDS/PAGE of proteins following import of in vitro synthesized RB47 protein into isolated pea chloroplast. ³⁵S-Met-labeled RB47 produced by in vitro translation (IVT RB47) was incubated with ATP and isolated pea chloroplasts. Chloroplasts were repurified by gradient centrifugation following incubation (+ chloroplast). Treatment with thermolysin prior to repurification (+ protease) degraded proteins not imported into the chloroplasts resulting in the loss of larger molecular mass proteins, but not in the loss of the 47-kDa protein. IVT of luciferase mRNA resulted in the production of a 48-kDa protein (IVT luc) that did not import or associate with repurified pea chloroplasts (+ chloroplast). IVT of RuBPCase small subunit mRNA produced a protein (IVT SSu) that imported efficiently in isolated pea chloroplast (+ chloroplast) and was protected from protease treatment (+ protease). Molecular mass is indicated at left.