Molecular Dynamics of the binding mode of substrate and inhibitor to CYP125 of Mycobacterium tuberculosis

DIANA MARTÍNEZ; PABLO E. ROSI; PAU ARROYO MAÑEZ

Sierra de la Ventana

Congreso; XLIII Reunión Anual SAB 2014; 2014

Sociedad Argentina de Biofísica

One of the most potential candidates for drug targeting in M. tuberculosis is the cytochrome P450 CYP125, an enzyme that has been recently demonstrated to catalyze the hydroxylation of cholesterol in its terminal C27 side chain (Capyk et al, 2009). The crystal structure revealed a ?letterbox?-like hydrophobic active site cavity that narrows in a funnel-like manner on approach to the heme center (McLean et al, 2010). The catalytic activity of CYP125 is necessary for the parasite surviving in its inner cell phase. Thus, the understanding of the catalytic mechanism would contribute to design better CYP125 inhibitors. Looking forward to having a view of the catalytic cycle as well as the mechanism of the inhibition activity classical molecular dynamic simulations in presence of its natural substrate cholesterol and the co-crystallized inhibitor cholest-4-en-3-one (K2B) (Ouellet et al, 2010) were performed. Three significant states were modeled: deoxygenated, oxygenated and ferryle state according to the mechanism proposed by Ouellet et al, 2010. All the modeled systems remained stable during the simulation time. Comparative analysis revealed similar binding modes for both ligands in all systems, showing that the side chain of cholesterol and K2B remains near the heme group. Also in both cases, hydrogen bond network between residues, D90 and K196, and the hydroxyl or keto groups were monitored for the cholesterol and K2B, respectively. Electrostatic interaction between the carboxylate and amino groups of D90 and K196, respectively, seems to be responsible for ligand stabilization as well as for the opening of the cavity, and therefore, for ligand entrance and exit from the enzymatic active site.