title: Aminoacylation of initiator methionyl-tRNA(i) under conditions inhibitory to initiation of protein synthesis.
abstract: Inhibition of protein synthesis in perfused rat liver deprived of either methionine or tryptophan results from a defect in peptide-chain initiation. Similarly, the decreased rate of protein synthesis in liver from rats deprived of food for 24 h and in skeletal muscle after 2 days of diabetes results from a defect in initiation. In the present study, the tissue content of tRNA(iMet) and its level of aminoacylation were measured in these conditions to determine whether methionyl-tRNA(iMet) formation is a mechanism involved in the regulation of initiation. The extent of aminoacylation of tRNA(iMet) in livers perfused with supplemented medium or medium deficient in either methionine or tryptophan was 64 +/- 2, 61 +/- 3, and 66 +/- 2% of the total accepting activity, respectively. The total tissue content of tRNA(iMet), expressed as a percentage of total RNA, was 1.7 +/- 0.1, 1.6 +/- 0.1, and 1.6 +/- 0.1 for the three conditions, respectively. In livers from starved rats, the extent of aminoacylation of tRNA(iMet) was 80 +/- 7% and the total tissue content of tRNA(iMet) was 1.9 +/- 0.1% compared with control values of 82 +/- 6 and 2.0 +/- 0.1%, respectively. In skeletal muscle from diabetic rats, the extent of aminoacylation of tRNA(iMet) was 79 +/- 4% and the total tissue content of tRNA(iMet) was 2.0 +/- 0.3% compared with values of 79 +/- 5 and 2.0 +/- 0.2% for control animals.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey 17033.
authors.forename: K M
authors.initials: KM
authors.lastname: Ojamaa
authors.forename: S R
authors.initials: SR
authors.lastname: Kimball
authors.forename: L S
authors.initials: LS
authors.lastname: Jefferson
mesh_terms: D000215:Acylation; D000596:Amino Acids / Q000172:deficiency; D000818:Animals; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D005508:Food Deprivation / Q000502:physiology; D008099:Liver / Q000378:metabolism; D008297:Male; D009132:Muscles / Q000378:metabolism; D011506:Proteins / Q000037:antagonists & inhibitors*; D012358:RNA, Transfer, Met / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000596:Amino Acids; D015852:Eukaryotic Initiation Factor-2; D011506:Proteins; D012358:RNA, Transfer, Met