Covalent attachment of fluorescent probes to the X-base of Escherichia coli phenylalanine transfer ribonucleic acid

Abstract
Was labeled with the N-hydroxysuccinimide esters of 1-dimethylaminaphthalene-5-sulfonyl glycine and N-methylanthranilic acid through reaction with the amino acid moiety of its X-base, whereby yields of 66% and 24%, respectively, were obtained. The purified dimethylaminonaphthalene-sulfonate derivative could not be aminoacylated and was found to a strong competitive inhibitor of phenyialanine-tRNA synthetase [Ki=8×10−7 M]. The N-methylanthraniloyl could be charged to an exten of 5% as compared to native tRNAPhe. The fluorescence emission spectra of the derivatives are indicative of a slightly hydrophobic environment for both fluorophores. The results suggest that the integrity of the polar amino acid group of the X-base is required for the maintenance of the biologically active conformation.