Studies on methyl-deficient methionine transfer ribonucleic acid from Escherichia coli.

Multiple functions of methyl-deficient tRNAMet, including those specific for initiator tRNA, were investigated and compared with normal tRNAMet. A comparison of the chromatographic properties of normal and methyl-deficient methionyl-tRNA showed identical elution profiles on methylated albumin-Kieselguhr, benzoylated o-(diethylaminoethyl)cellulose, and reverse phase chromatography (isoamylacetate) columns, but resolved a unique peak of methyl-deficient methionyl-tRNA on a reverse phase chromatography (Freon) column. We were unable to recover active pure methyl-deficient tRNA from this column, so that most subsequent studies had to be done on unfractionated methyl-deficient tRNA preparations. The only abnormality noted for methyl-deficient tRNAMet was a low velocity of acylation for the unique methyl-deficient peak. This was exhibited by examining the different patterns obtained on reverse phase chromatography for partially acylated compared to fully acylated tRNAMet. In all other ways tested the methyl-deficient tRNAMet functioned normally. Coding with AUG and GUG triplets was indistinguishable from normal as was the stimulation of this binding by purilied initiation factors. Extent and rate of formylation, exclusion from recognition by bacterial elongation factors and function in NHz-terminal dipeptide synthesis all appeared to be normal in the methyl-deficient tRNA. Of peripheral interest was the finding that tRNAget appears to be acylated about 2.2 times more rapidly by purified methionyl-tRNA synthetase than tRNAret.