Synthesis of ribulose 1,5—bisphosphate carboxylase by isolated Sorghum mesophyll chloroplasts.

ABSTRACT

Chloroplasts isolated from Sorghum vulgare are active in light-dependent, organelle protein synthesis. Intact chloroplasts can use light as an energy source; photosynthetically inactive chloroplasts require the addition of ATP for this protein synthesis. P reincubation of chloroplasts in light at 25°C for 1 h depleted the endogenous templates completely; such preincubated chloroplasts translated exogenously added heterologous templates efficiently. When total cellular RNA from Chlorella protothecoides, a C3 plant, was used as template for translation in a cell-free light-dependent system of isolated mesophyll chloroplasts from Sorghum vulgare, a C4 type plant, polypeptides of 55 kDa (large subunit) and 15 kDa (small subunit) were detectable in the fluorographic profile of the newly synthesized proteins; these polypeptides were absent in the products obtained with endogenous RNA. Evidence for the fidelity of the system was obtained by immunological arenlallay sis of ribulose 1, 5-bisphosphate carboxylase obtained by the translation of Chlo Acesl.l ular RNAs.