Covalent complex of phenylalanyl‐tRNA synthetase with 4‐thiouridine‐substituted tRNAPhe gene transcript retains aminoacylation activity1

Abstract
S4U‐containing transcripts of tRNAPhe gene have been prepared by complete substitution of 16 U residues or by random incorporation of s4U residues followed by affinity electrophoresis isolation of s4U‐monosubstituted tRNA transcripts. Both analogs have been cross‐linked to Thermus thermophilus phenylalanyl‐tRNA synthetase (PheRS) and the specificity of the cross‐linking has been demonstrated. Functional activity of the covalent complex of PheRS with the s4U‐monosubstituted transcript has been shown by aminoacylation of 60% of the enzyme‐cross‐linked tRNA. This is the first instance in which biological activity of aminoacyl‐tRNA synthetase and cross‐linked tRNA in a specific complex has been revealed.