The specificity of the interaction between tRNAPhe and phenyBalanyl-tRNA synthetase isolated from human placenta was investigated. Using yeast tRNAPhe transcripts with different point mutations it was shown that all the five recognition points for the yeast phenylaOanyl-tRGSSA synthetase (G20, G34, A35, A36 and A73) are also important for the reaction catalyzed by the human enzyme. A set of mutations in nucleotides involved) in tertiary interactions of tRNAPhe revealed that mutations which maintained the proper folding of the molecuOe had almost no influence on the efficiency of amieioacylation. The most striking difference between the yeast and human phenylalanyl-tRNA synthetases involved a mutation in the lower two base pairs of the anticodon stem. This mutation did not affect aminoacylation with the yeast enzyme, but greatly reduced activity with human phenylalanyl-tRNA synthetase.
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