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

Abstract
The structural features of the G⋅U wobble pair in Escherichia coli alanine transfer RNA (tRNA Ala ) that are associated with aminoacylation by alanyl-tRNA synthetase (AlaRS) were investigated in vivo for wild-type tRNA Ala and mutant tRNAs with G⋅U substitutions. tRNA Ala with G⋅U, C⋅A, or G⋅A gave similar amounts of charged tRNA Ala and supported viability of E. coli lacking chromosomal tRNA Ala genes. tRNA Ala 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.