Fluorescence-monitored conformational change on the 3 '-end of tRNA upon aminoacylation

Fluorescent tRNAs species with formycine in the T-terminal position (tRNA-C CF) were derived from Escherichia coli tRNA(Val), Thermus thermophilus tRNA (Asp) and Thermus thermophilus tRNA(Phe). The fluorescence of formycine was used to monitor the conformational changes at the 3'-terminus of tRNA caus ed by aminoacylation and hydrolysis of aminoacyl residue from aminoacyl-tRN As. An increase of about 15% in the fluorescence intensity was observed aft er aminoacylation of the three tRNA-CCF. This change in fluorescence amplit ude that is reversed by hydrolysis of the aminoacyl residue, does not depen d on the structure of the amino acid or tRNA sequence. A local conformation al change at the 3'-terminal formycine probably involving a partial destack ing of the base moiety in the ACCF end takes place as a consequence of amin oacylation. A structural change at the 3'-terminus of tRNA induced by attac hment and detachment of the acyl residue may be important in controlling th e substrate/product relationship in reactions in which tRNA participates du ring protein biosynthesis.