Studies on the effect of ethanol on eukaryotic protein synthesis in vitro.

The effects of varying concentrations of ethanol on reactions involved in protein biosynthesis have been examined using a cell-free system from Chinese hamster ovary cells that actively translates natural mRNAs in order to detect those components most sensitive to alcohol. Ethanol, at relatively low concentrations (0.2 M or lower) inhibited the translation of endogenous polysomal mRNAs and, in mRNA-depleted extracts, of exogenous natural mRNA. Ethanol markedly inhibited leucyl-tRNA synthetase, and it inhibited Phe- and Glu-tRNA synthetases to some extent, but had only a small effect on several other aminoacyl-tRNA synthetases, elongation factors 1 and 2, ribosomes, or the formation of eukaryotic initiation factor 2 . GTP . Met-tRNAr ternary complex. Methanol inhibited slightly the translation of mRNA and Leu-tRNA synthetase, but isobutyl alcohol and isopropyl alcohol strongly depressed these activities. Ethanol inhibited the interaction of leucine with Leu-tRNA synthetase competitively, whereas isobutyl alcohol and acetaldehyde inhibited the leucine interaction in a noncompetitive manner. Leu-tRNA synthetase from Chinese hamster ovary cells was more sensitive to ethanol than that from yeast.