Protein Synthesis in Isolated Mitochondria of Rice (Oryza sativa L.) Seedlings

For studies of in organello mitochondrial protein synthesis in rice, Oryza sativa L., conventional surface-sterilization procedures were demonstrated to be ineffective. Because of the over-whelmingly efficient [(35)S]methionine utilization by contaminating bacteria, even "essentially bacteria-free" rice mitochondria were shown to be unsuitable for the study of in organello protein synthesis. We developed a procedure to obtain a bacteria-free preparation of rice mitochondria. Such mitochondria favored a membrane-dependent ATP-generating system over an external ATP-generating system as the energy supplement for in organello protein synthesis. Two distinct classes of [(35)S]methionine-labeled, cycloheximide-insensitive products were detected: an electrophoretically unresolved population and a set of some 22 to 27 discrete polypeptide species, each with a characteristic electrophoretic mobility and relative abundance.