Mechanistic insights from molecular dynamic simulation of Rv0045c esterase in Mycobacterium tuberculosis

Rv0045c is an esterase involved in lipid metabolism of Mycobacterium tuberculosis. It belongs to the α/β hydrolase family. In the current study, we performed sequence- and structure-based analysis of Rv0045c followed by molecular dynamics (MD) simulation for 100 ns to investigate conformational changes in the enzyme. Sequence analysis revealed that this enzyme is possibly a hormone-sensitive lipase. Further, through structural analysis, a putative catalytic tetrad containing "Ser-Asp-Ser-His" and residues involved in the formation of an oxyanion hole were identified. MD simulation of Rv0045c revealed a conformational transition from an open to a closed state. The active site pocket was found to be gated by four loops. The potential role of the cap domain and the mobile histidine is discussed. From the simulation, we see that the conformational changes mimic the different stages in the reaction mechanism of Rv0045c. These results support the hypothesis that free enzyme simulation encompasses all the conformations necessary for the different stages of catalysis. Our findings add to the growing knowledge of an important family of esterases in Mycobacterium tuberculosis.