title: Protein synthesis and aging: studies with cell-free mammalian systems.
abstract: A cell-free system devoid of polysomes, which translates natural mRNA, has been prepared from rat liver. It contains ribosomal subunits, ribosomes, aminoacyl-tRNA synthetases, tRNAs, and protein factors necessary for translation. Protein synthesis required an energy-generating system, mRNA, and 3 mM Mg2+ concentration, and it was inhibited by 7-methylguanylic acid. The total extent and the rate of protein synthesis were approximately 30% greater when the translating system was prepared from livers of 3-month-old rats, as compared to 30-month-old rats. A ribosome-free fraction containing the protein factors required for translation was also prepared from 3-month-old and 30-month-old rat livers and brains, by extraction with 0.5 M KCl. The high-salt extracts were analyzed for elongation factors EF-1 and EF-2 in a poly(U) translating system. Although the activity of EF-2 was similar in preparations from young and old rats, the EF-1 activity in the 3-month-old rat livers and brains was 30 to 40% greater than in 30-month-old animals. The protein synthesizing activity of high salt-washed ribosomes stripped of endogenous peptidyl-tRNA and mRNA, from livers and brains of young and old animals, was the same.
mesh_terms: D000375:Aging; D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000648:ultrastructure; D008099:Liver / Q000648:ultrastructure; D010441:Peptide Chain Elongation, Translational; D010442:Peptide Chain Initiation, Translational; D010445:Peptide Elongation Factors / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism; D051381:Rats; D012261:Ribonucleoproteins / Q000096:biosynthesis; D012270:Ribosomes / Q000378:metabolism
chemical_list: D010445:Peptide Elongation Factors; D010448:Peptide Initiation Factors; D012333:RNA, Messenger; D012261:Ribonucleoproteins; D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases