Photoaffinity reagents for modification of aminoacyl-tRNA synthetases

Up to now, a few derivatives of aminoacyl-tRNA with a reactive group attached to the aminoacyl residue [l-4] and a reactive analog of an amino acid [4] have been used for the affinity labeling of aminoacyltRNA synthetases (EC 6.1 .l). For detailed investigation of the active centers of these enzymes, it is necessary to prepare tRNA analogs bearing reactive group at some other sites of the tRNA molecule, as well as reactive ATP analogs. The present communication describes ATP and tRNA analogs containing a photoreactive azido group, namely ATP-y-p-azidoanilide and tRNA containing the Ns Cg Ha NH-CO-CH2 -group at iached to a 4thiouridine residue. The possibility of using the photoreactivity of the 4-thiouridine residue of tRNA for photoaffinity labeling of phe-RSase* is also reported; a similar approach has been proposed by other workers [6] who described a light induced reaction of 4-thiouridine triphosphate with RNA polymerase.