Functional analyses of dipeptide and pentapeptide insertions on Theileria annulata enolase by site-directed mutagenesis and in silico approaches

Abstract

Theileria annulata enolase (TaENO) could be assessed as a druggable target for tropical theileriosis treatment. The parasite enzyme plays an important role in many cellular functions and carries some structural differences like dipeptide (262EK263) and pentapeptide ((103)EWGYC(107)) insertions from the host enzyme, Bos taurus enolase. In this study, the functional effects of these insertions on TaENO activity were analyzed by in vitro site-directed mutagenesis and in silico molecular docking analyses for the first time in the literature. In vitro results showed that, although the deletion of the pentapeptide insertion (TaENO Delta EWGYC) reduced the enzyme activity slightly, the removal of the dipeptide insertion (TaENO Delta EK) halted it. Also, molecular docking results revealed that the deletion of these insertions affected the substrate binding affinity of the mutant enzymes. The active site of TaENO Delta EK exhibited a small decrease of substrate binding affinity compared to the active site of TaENO Delta EWGYC relative to the wild type TaENO. Although we conclude that both regions could be evaluated as possible drug-binding sites to inhibit TaENO in further studies, these results indicate that the dipeptide insertion could be a more promising drug binding site than the pentapeptide insertion.