title: Mammalian mitochondrial ribosomes. Studies on the exchangeability of polypeptide chain elongation factors from bacterial and mitochondrial systems.
abstract: Mammalian mitochondrial ribosomes from rat liver synthesised poly(phenylalanine) from [14C]-Phe-tRNA in the presence of a homologous 10(5) X gav supernatent fraction. The activity depended on the addition of synthetic template and was resistant to cycloheximide. The polyanion spermidine had a stimulatory effect on peptide synthesis in vitro. In contrast to Escherichia coli ribosomes, which also functioned with heterologous supernatant fractions, 55-S mitochondrial ribosomes were inactive when supplemented with heterologous supernatant fractions from E. coli or with purified bacterial elongation factors. EF-T slightly stimulated polyphenylalanine synthesis when added in combination with mitochondrial supernatant fractions. Two-dimensional electrophoretic analysis of the protein content of both supernatant fractions revealed considerable differences in the distribution of the species-specific proteins according to their isoelectric points. The mitochondrial supernatant proteins were in general more basic, and the few acidic proteins did not co-migrate with EF-Tu or EF-G from E. coli.
mesh_terms: D000818:Animals; D004587:Electrophoresis, Agar Gel; D004926:Escherichia coli / Q000378:metabolism*; D005260:Female; D008930:Mitochondria, Liver / Q000378:metabolism*; D010452:Peptide Biosynthesis; D010445:Peptide Elongation Factors / Q000378:metabolism*; D010649:Phenylalanine / Q000378:metabolism; D011072:Poly U / Q000378:metabolism; D012329:RNA, Bacterial / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism; D051381:Rats; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D010445:Peptide Elongation Factors; D012329:RNA, Bacterial; D011072:Poly U; D010649:Phenylalanine; D012343:RNA, Transfer