TRANSFER-RNA AMINOACYLATION - IDENTIFICATION OF A CRITICAL RIBOSE 2'-HYDROXYL-BASE INTERACTION

To understand the relationship between tRNA architecture and specific aminoacylation by aminoacyl-tRNA synthetases, we performed kinetic ass ays of Escherichia coli tRNA(Pro) molecules containing single deoxynuc leotide substitutions. We identified an important 2'-hydroxyl group at position U8 (of 22 positions probed). Chemical modification studies s howed that this 2'-hydroxyl interacts with either the N1 or the exocyc lic amine of G46 in a hydrogen bonding interaction that contributes 1. 8 kcal/mol to the free energy of activation for aminoacylation. Molecu lar modeling of tRNA(Pro) supports the existence of this interaction. This is the first study to identify a specific ribose 2'-hydroxyl-base interaction in the core region of a tRNA molecule that makes a thermo dynamically significant contribution to aminoacylation.