Genetic selection for active E.coli amber tRNA ^Asn exclusively led to glutamine inserting suppressors Open Access

Suppressor tRNAs are useful tools for determining identity elements which define recognition of tRNAs in vivo by their cognate aminoacyl-tRNA synthetases. This study was aimed at the isolation of active amber tRNA ^Asn . Nineteen mutated tRNA ^Asn_CUA having amber suppressor activity were selected by an in vivo genetic screen, and all exclusively inserted glutamine. From analysis of the different mutations it Is concluded that glutamine accepting activity was obtained upon reducing the interaction strength between the first base pair of thetRNA ^Asa_CUA by direct or Indirect effects. Failure to Isolate tRNA ^Asa_CUA suppressors charged with asparagine as well as other evolutionary related amino acids is discussed.