Charging of a Yeast Methionine tRNA with Phenylalanine and its Implication for the Synthetase Recognition Problem

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Abstract
The non-initiating yeast .**GRAPHIC**. has those regions in common with yeast tRNAPhe which were proposed by Roe, Dudock, et al; to be primarily involved in the recognition site for phenylalanyl-tRNA synthetase. Thus, a high degree and rate of mischarging of .**GRAPHIC**. with phenylalanine would be expected. Under standard conditions this misaminoacylation reached only 2% of homologous charging. Apparently, recognition by phenylalanyl-tRNA synthetase requires additional or alternative structural features in the tRNA. Since the hypothesis of Roe, Dudock, et al; was mainly based on kinetic measurements under so-called special aminoacylation conditions, experiments done under similar conditions were studied. Kinetic data on Phe-tRNAPhe formation and on the phenylalanine acceptance of Escherichia coli tRNAVal (included as a control), were nearly the same as those reported in the literature. Under the special conditions, misaminoacylation of .**GRAPHIC**. was raised to 65% of the homologous charging. The maximal velocity of misaminoacylation, however, was found to be considerably lower than that of the aminoacylation reaction of tRNAPhe. This finding is also incompatible with the above hypothesis.