This research explores the manner in which glycyl-tRNA synthetase recognizes and charges glycine-specific tRNA and makes an essential contribution to the process of protein biosynthesis. The work will employ site-specific labeling reagents which are chemical analogs of the normal substrates, tRNA and ATP, to locate domains within the enzyme essential to catalysis and to its biological function. The proposed experiments are aimed at obtaining amino acid sequences of peptide segments involved directly and in proximity to the enzyme's catalytic site. In these experiments, emphasis will be given to the dissimilar alpha and beta subunits comprising the enzyme. An effort will be made to determine how these subunits are arranged in the native enzyme, how they form or constrain its catalytic site, and how they cooperate in recognizing glycine-specific tRNA and reject non-cognate tRNA. In order to investigate the generality of these findings, it is proposed that some parallel experiments with phenylalanyl-tRNA synthetase be conducted. This enzyme is the only other synthetase which contains dissimilar subunits. This work will provide important information regarding the molecular mechanism of protein-RNA recognition and the manner in which the aminoacyl-tRNA synthetases are able to minimize error in the expression of genetic information in DNA.
