Yeast tRNA(Met) recognition by methionyl-tRNA synthetase requires determinants from the primary, secondary and...

The primordial role of the CAU anticodon in methionine identity of the tRNA has been established by others nearly a decade ago in Escherichia coli and yeast tRNA(Met). We show here that the CAU triplet alone is unable to confer methionine acceptance to a tRNA. This requires the contribution of the discriminatory base A73 and the non-anticodon bases of the anticodon loop. To better understand the functional communication between the anticodon and the active site, we analysed the binding and aminoacylation of tRNA(Met) based anticodon and acceptor-stem minihelices and of tRNA(Met) chimeras where the central core region of yeast tRNA(Met) is replaced by that of unusual mitochondrial forms lacking either a D-stem or a T-stem. These studies suggest that the high selectivity of the anticodon bases in tRNA(Met) implies the L-conformation of the tRNA and the presence of a D-stem. The importance of a L-structure for recognition of tRNA(Met) was also deduced from mutations of tertiary interactions known to play a general role in tRNA(Met) folding.