RESUMO
Leucyl-tRNA synthetases (LRS) catalyze the linkage of leucine with tRNALeu. A large insertion CP1 domain(Connective Polypeptide 1) in LRS is responsible for post-transfer editing of mis-charged aminoacyl-tRNAs.Here, we characterized the CP1 domain of Leishmania donovani, a protozoan parasite, and its role in editingactivity and interaction with broad spectrum anti-fungal, AN2690. The deletion mutant of LRS, devoid of CP1domain (LRS-CP1D) was constructed, followed by determination of its role in editing and aminoacylation.Binding of AN2690 and different amino acids with CP1 deletion mutant and full length LRS was evaluatedusing isothermal titration calorimetry (ITC) and molecular dynamics simulations. The recombinant LRS-CP1Dprotein did not catalyze the aminoacylation and the editing reaction when compared to full-length LRS. Thus,indicating that CP1 domain was imperative for both aminoacylation and editing activities of LRS. Bindingstudies with different amino acids indicated selectivity of isoleucine by CP1 domain over other amino acids.These studies also indicated high affinity of AN2690 with the editing domain. Molecular docking studiesindicated that AN2690-CP1 domain complex was stabilized by hydrogen bonding and hydrophobic interactions resulting in high binding affinity between the two. Our data suggests CP1 is crucial for the function of L.donovani LRS.
RESUMO
Purpose To clone and express Trypanosoma Leucyl-tRNA synthetase (LeuRS) gene and to complete the purification and activity assay of LeuRS. Methods We cloned the LeuRS gene from T. Brucei genomic DNA,and cloned it into pBS-T and then into the expression vector pET21a( + ) .The expression of T. Brucei LeuRS was carried out in E. coli BL21 (DE3) RIPL host by optimizing the expression conditions. The products are purified by His-Bind affinity column and verified by Western blot . Enzymatic activity was detected by isotope labeling. Results A DNA fragment at length of 3.2 kb was amplified. Both restriction analysis and sequencing analysis proved that recombinant plasmid pET21a( + )/LeuRS was correctly constructed. The expressed product contained about 20% of total somatic soluble protein and reached a purity of 85% after purification . It was verified by the Western blot. Enzyme unit per millilitre of purified products was about 72. Conclusion Here we report the successful clone, expression and purification of LeuRS from Trypanosoma Brucei ( T. Brucei) in bacterial host. In addition, we tested its enzymatic activity by isotope labeling.This work would be helpful to the design and in vitro screening of Trypanosoma LeuRS inhibitors.