title: Isoleucyl initiator tRNA does not initiate eucaryotic protein synthesis.
abstract: Initiator tRNA from yeast (tRNAMeti) was quantitatively misaminoacylated with L-isoleucine using isoleucyl-tRNA synthetase from Escherichia coli. Surprisingly the misaminoacylated Ile-tRNAMeti neither participates in nor inhibits the initiation of globin synthesis in a rabbit reticulocyte lysate, whereas Met-tRNAMeti readily initiates protein synthesis in the same system. The incompetent behavior of Ile-tRNAMeti may be related to the observation that in vitro it does not form a stable complex with eucaryotic initiation factor 2 (eIF-2) and GTP, under conditions which lead to a stable eIF-2 X GTP X Met-tRNAMeti ternary complex. This indicates that eIF-2 can discriminate between the side chains of the aminoacyl adducts of the tRNAMeti during ternary complex formation, the first essential step in initiation of eucaryotic protein synthesis.
mesh_terms: D000818:Animals; D004926:Escherichia coli / Q000201:enzymology; D015852:Eukaryotic Initiation Factor-2; D006160:Guanosine Triphosphate / Q000378:metabolism; D007532:Isoleucine / Q000378:metabolism; D007533:Isoleucine-tRNA Ligase / Q000378:metabolism; D007700:Kinetics; D010442:Peptide Chain Initiation, Translational; D010448:Peptide Initiation Factors / Q000378:metabolism; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism
chemical_list: D015852:Eukaryotic Initiation Factor-2; D010448:Peptide Initiation Factors; D011506:Proteins; D012346:RNA, Transfer, Amino Acyl; C026464:tRNA(m)(Met), methionine-; D007532:Isoleucine; D006160:Guanosine Triphosphate; D007533:Isoleucine-tRNA Ligase