Crucial role of the C-terminal domain of Mycobacterium tuberculosis leucyl-tRNA synthetase in aminoacylation and editing

Abstract

The C-terminal extension of prokaryotic leucyl-tRNA synthetase (LeuRS) has been shown to make contacts with the tertiary structure base pairs of tRNA^Leu as well as its long variable arm. However, the precise role of the flexibly linked LeuRS C-terminal domain (CTD) in aminoacylation and editing processes has not been clarified. In this study, we carried out aspartic acid scanning within the CTD of Mycobacterium tuberculosis LeuRS (MtbLeuRS) and studied the effects on tRNA^Leu-binding capacity and enzymatic activity. Several critical residues were identified to impact upon the interactions between LeuRS and tRNA^Leu due to their contributions in the maintenance of structural stability or a neutral interaction interface between the CTD platform and tRNA^Leu elbow region. Moreover, we propose Arg921 as a crucial recognition site for the tRNA^Leu long variable arm in aminoacylation and tRNA-dependent pre-transfer editing. We also show here the CTD flexibility conferred by Val910 in regulation of LeuRS–tRNA^Leu interaction. Taken together, our results suggest the structural importance of the CTD in modulating precise interactions between LeuRS and tRNA^Leu during the quality control of leucyl-tRNA^Leu synthesis. This system for the investigation of the interactions between MtbLeuRS and tRNA^Leu provides a platform for the development of novel antitubercular drugs.