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The photoinduced reaction of phenylalanyl-tRNA synthetase (B.C. 6.1.1.20) from E.coli MRE-600 with tRNAAPhe containing photoreative p-N3-C6H4-NJHCOCH2-group attached to 4-thiouridine sU8 (azido-tRNAAPhe) was investigated. inhibitio of the photoinduced reaction. Therefore, the reaction of [14c -Phe-azido-tRNA with the enzyme is significantly less sensitive to the presence of the ligands than the reaction of chlorambucilyl-tRNA with the reactive group attached to the acceptor end of the tRNA studied in 1. It has been concluded that the kinetics of the affinity labelling does permit to discriminate the influence of the low molecular weight ligands of the enzyme on the different sites of the tRNAenzyme interaction.

A simple and rapid column procedure is described for the isolation from protein hydrolysates of peptides containing covalently bound substrate analogues with cis-diol groups. The method is based on complex formation between the cis-diol groups of peptide-bound compounds and dihydroxyborylic groups of a dihydroxyborylaminoethyl cellulose column. The method is useful for isolation of peptide(s) located in or near the active centre of enzymes after their affinity labelling by chemically active analogues of natural substrates like ribonucleotides, sugars, etc.