Protein synthesis in chloroplasts: V. Translation of messenger RNA for the large subunit of fraction I protein in a heterologous cell-free system

The addition of spinach chloroplast total RNA to cell-free extracts from Escherichia coli stimulates amino acid incorporation into protein. The products were characterized by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, and were qualitatively and quantitatively similar to those synthesized in intact isolated chloroplasts. There are two major discrete products of both systems with molecular weights of 52,000 and 35,000. The [ 35S]methionine-containing chymotryptic peptides of the 52,000 M r polypeptide synthesized in the E. coli cell-free system have been compared with those of fraction I protein large subunit labelled with [ 35S]methionine in vivo. From the close similarity in chromatographic properties of the peptides of the two polypeptides, we conclude that the 52,000 M r product of chloroplast RNA-directed protein synthesis in E. coli extracts is the large subunit of fraction I protein.