title: The effect of non-permissive temperature on met-tRNA synthetase in Saccharomyces cerevisiae temperature-sensitive mutant ts 7-45.
abstract: The effects of incubation of yeast spheroplasts at elevated temperature (40 degrees C) on a number of activities involved in protein biosynthesis have been examined in preparations obtained from wild-type cells (wt A364A ) and a temperature-sensitive mutant (ts 7-45) derived from it. With wild-type cells, preincubation of spheroplasts at the elevated temperature had little or no effect on the following: the ribosomal subunit-polysome pattern; the translation of exogenous natural mRNA in postpolysomal extracts devoid of endogenous mRNA; the translation of poly(U) in postpolysomal extracts; the incorporation of methionine into 40 S preinitiation and 80 S initiation complexes; the synthesis of Met-tRNA in postribosomal (cytosol) extracts; and the formation of eIF-2 X GTP X Met-tRNAf ternary complex in the cytosol. With temperature-sensitive spheroplasts that had not been preincubated at the elevated temperature, the concentration of free, native 40 S subunits appeared to be lower and that of 60 S subunits higher than in wild-type cells; translation of exogenous natural mRNA in postpolysomal extracts was somewhat lower than in wild-type preparations, but all of the other reactions and components measured were comparable to those in wild-type preparations. Preincubation of temperature-sensitive spheroplasts at 40 degrees C resulted in: a further decrease in the level of 40 S subunits; disaggregation of polysomes; loss of ability to translate natural mRNA but not poly(U); decreased ability to form 40 S preinitiation intermediates; and production of an activity, found in the cytosol, that inhibited Met-tRNA synthetase reversibly. The inhibitor had the characteristics of a protein and did not appear to be a proteinase, nuclease, or nucleotidase.
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D007700:Kinetics; D008718:Methionine-tRNA Ligase / Q000378:metabolism*; D009154:Mutation; D011061:Poly A / Q000235:genetics; D011132:Polyribosomes / Q000201:enzymology; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D013104:Spheroplasts / Q000201:enzymology; D013696:Temperature
chemical_list: D012333:RNA, Messenger; D011061:Poly A; D000604:Amino Acyl-tRNA Synthetases; D008718:Methionine-tRNA Ligase