tRNA selection by a class II aminoacyl-tRNA synthetase: the role of accessory domains and inter-domain communication in RNA recognition.

We have used a secondary site suppression approach to investigate the basis of tRNA selection by the E. coli histidyl-tRNA synthetase. This enzyme recognizes a unique G-1:C73 base pair located in the acceptor stems of prokaryotic histidyl-tRNAs. A genetic selection system was constructed in which growth on glycerol was dependent on histidine specific amber suppression of a triose phosphate isomerase (tpi) gene containing an amber codon at His 95. Three independent revertants linked to hisS were isolated and sequenced, and the resulting mutant proteins were characterized biochemically. These studies are interpreted in light of the x-ray structure of the E. coli HisRS adenylate complex, and show that the C-terminal domain and its interactions with the catalytic domain play a biologically significant role in tRNA selection.