[Specific modification of phenylalanine:tRNA-ligases of E. coli MRE-600 with N-chlorambucilyl-14c-phenylalanyl-tRNA]

Abstract

N-Chlorambucilyl-[14C]phenylalanyl-tRNA was used for the affinity modification of phenylalanine : tRNA-ligase from E. coli MRE-600. It has been found that N-chlorambucilyl-[14C]phenylalanyl-tRNA selectively inactivates phenylalanine : tRNA-lagase that results in formation of a covalent bond between the tRNA derivative and the enzyme at pH 5.8, 25 degrees C. The rate fall of the aminoacylation of tRNA with [14C]phenylalanine was observed after the enzyme incubation with N-chlorambucilyl-[14C]phenylalanyl-tRNA at pH 7.5, 25 degrees C. It has been shown that this modification results in a similar rate decrease of tRNA aminoacylation with [14C]phenylalanine, ATP-[32P]pyrophosphate exchange and reaction of the enzymatic deacylation of [14C]phenylalanyl-tRNA. This fact evidences in favour of the possibility of the alkylation to proceed in the proximity of the active centre of the enzyme. The covalent complex obtained seems to be an interesting model for the studies of the mechanisms involved in tRNA aminoacylation as well as for elucidation of the tertiary structure of tRNA bound with the enzyme.