Functional Evidence for Indirect Recognition of G·U in tRNAAla by Alanyl-tRNA Synthetase

The structural features of the G·U wobble pair in Escherichia coli alanine transfer RNA (tRNAAla) that are associated with aminoacylation by alanyl-tRNA synthetase (AlaRS) were investigated in vivo for wild-type tRNAAla and mutant tRNAs with G·U substitutions. tRNAAla with G·U, C·A, or G·A gave similar amounts of charged tRNAAla and supported viability of E. coli lacking chromosomal tRNAAla genes. tRNAAla with G·C was inactive. Recognition of G·U by AlaRS thus requires more than the functional groups on G·U in a regular helix and may involve detection of a helical distortion.