title: Mitochondrial protein synthesis in HeLa cells.
abstract: HeLa cell mitochondrial proteins have been shown to be the products of two separate protein-synthesizing systems; one, the general cellular mechanism, sensitive to inhibition by cycloheximide, the other, a specific mitochondrial system subject to inhibition by low concentrations of chloramphenicol (Galper, J. B., and J. E. Darnell. 1971. J. Mol. Biol 57:363). Preliminary data have suggested that a mitochondrial N-formyl-methionyl-tRNA (f-Met-tRNA) might be the initiator tRNA in the latter (Galper, J. B., and J. E. Darnell. 1969. Biochem. Biophys. Res. Commun. 34:205; 1971. J. Mol. Biol. 57:363). It is demonstrated here that the synthesis of these endogenous mitochondrial proteins is also subject to inhibition by ethidium bromide and decays with a half-life of 1(1/2)-2 h in cultures incubated with low concentrations of this dye. The role of formylated f-Met-tRNA as the initiator tRNA in the synthesis of mitochondrial proteins is supported by data from several experiments. The rates of ethidium bromide inhibition of both the charging of f-Met-tRNA and of the synthesis of mitochondrial proteins are strikingly similar. Inhibition by aminopterin of the formylation of f-Met-tRNA greatly depresses the rate of mitochondrial-specific protein synthesis. In the absence of the synthesis of these proteins, respiration, the levels of cytochromes a-a(3) and b, and the number of mitochondrial cristae are decreased. The implications of these findings as they relate to mitochondrial biogenesis are discussed.
mesh_terms: D000630:Aminopterin / Q000494:pharmacology; D002250:Carbon Radioisotopes; D002499:Centrifugation, Density Gradient; D002701:Chloramphenicol / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003580:Cytochromes / Q000378:metabolism; D004351:Drug Resistance; D004591:Electrophoresis, Polyacrylamide Gel; D004996:Ethidium / Q000494:pharmacology; D005561:Formates / Q000378:metabolism; D006207:Half-Life; D006367:HeLa Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D007930:Leucine; D008715:Methionine; D008928:Mitochondria / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D010101:Oxygen Consumption; D012343:RNA, Transfer / Q000378:metabolism; D013053:Spectrophotometry; D013997:Time Factors; D014316:Tritium
chemical_list: D002250:Carbon Radioisotopes; D003580:Cytochromes; D005561:Formates; D009363:Neoplasm Proteins; D014316:Tritium; D002701:Chloramphenicol; D012343:RNA, Transfer; D003513:Cycloheximide; D008715:Methionine; D004996:Ethidium; D007930:Leucine; D000630:Aminopterin