Analogs of methionyl-tRNA synthetase substrates containing photolabile groups

Three photolabile analogs of substrates of methionyl-tRNA synthetase were synthesized. In one, the 4-thiouridine at the 8 position of E. coli tRNAfMet was alkylated with [14C]p-azidobromoacetanilide. In the second, [14C]p-azidobenzoic acid hydrazide was condensed with the 3'-terminal dialdehyde of periodate-oxidized Escherichia coli tRNAfMet. The modified tRNAs could be purified by chromatography on benzoylated DEAE-cellulose. The third photolabile compound was [3H]methioninyl-8-azido-adenosine 5'-phosphate, an analog of the methionyl adenylate intermediate in the aminoacylation reaction. Irradiation of each of these compounds in the presence of equimolar amounts of E. coli methionyl-tRNA synthetase of micrometer concentrations gave 5-15% crosslinking.