FIG. 1.

Light-regulated translation in mature chloroplasts isolated from C. reinhardtii cells. Intact C. reinhardtii cw15 chloroplasts were collected from a 45%/70% interface of discontinuous Percoll gradient by published methods (4, 22). Intact chloroplasts were incubated in the dark for 30 min, and an aliquot was transferred for 10 min into the light (150 μmol m⁻² s⁻¹). The translational activities of the dark-incubated (D) and light-incubated (L) chloroplasts were then assayed by labeling newly synthesized proteins for 10 min with [³⁵S]methionine. The nascent polypeptides were allowed to complete synthesis by incubation for an additional 5 min in the presence of excess nonradioactive methionine. Chloroplasts were lysed, and extracted proteins were fractionated by SDS-PAGE and blotted onto nitrocellulose membranes. (A) Amido Black staining of chloroplast proteins. (B) Autoradiograph of the same blot as in panel A showing the ³⁵S-labeled proteins. LSU, large subunit of ribulose bisphosphate carboxylase/oxygenase.