FUNCTIONAL EVIDENCE FOR INDIRECT RECOGNITION OF G-CENTER-DOT-U IN TRNA(ALA) BY ALANYL-TRANSFER-RNA SYNTHETASE

The structural features of the G . U wobble pair in Escherichia coli a lanine transfer RNA (tRNA(Ala)) that are associated with aminoacylatio n by alanyl-tRNA synthetase (AlaRS) were investigated in vivo for wild -type tRNA(Ala) and mutant tRNAs with G . U substitutions. tRNA(Ala) w ith G . U, C . A, or G . A gave similar amounts of charged tRNA(Ala) a nd 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.