ACCEPTOR STEM AND ANTICODON RNA HAIRPIN HELIX INTERACTIONS WITH GLUTAMINE TRANSFER-RNA SYNTHETASE

The class I glutamine (G1n) tRNA synthetase interacts with the anticod on and acceptor stem of glutamine tRNA. RNA hairpin helices were desig ned to probe acceptor stem and anticodon stem-loop contacts. A seven-b ase pair RNA microhelix derived from the acceptor stem of tRNA(G1n) wa s aminoacylated by G1n tRNA synthetase. Variants of the glutamine acce ptor stem microhelix implicated the discriminator base as a major iden tity element for glutaminylation of the RNA helix. A second RNA microh elix representing the anticodon stem-loop competitively inhibited tRNA (G1n) charging. However, the anticodon stem loop microhelix did not en hance aminoacylation of the acceptor stem microhelix. Thus, transducti on of the anticodon identity signal may require covalent continuity of the tRNA chain to trigger efficient aminoacylation.