Exploring the Molecular Basis of Qo bc1 Complex Inhibitors Activity to Find Novel Antimalarials Hits.

Cytochrome bc1 complex is a crucial element in the mitochondrial respiratory chain, being indispensable for the survival of several species of Plasmodia that cause malaria and, therefore, it is a promising target for antimalarial drug development. We report a molecular docking study building on the most recently obtained X-ray structure of the Saccharomyces cerevisiae bc1 complex (PDB code: 3CX5) using several reported inhibitors with experimentally determined IC50 values against the Plasmodium falciparum bc1 complex. We produced a molecular docking model that correlated the calculated binding free energy with the experimental inhibitory activity of each compound. This Qo model was used to search the drug-like database included in the MOE package for novel potential bc1 complex inhibitors. Twenty three compounds were chosen to be tested for their antimalarial activity and four of these compounds demonstrated activity against the chloroquine-resistant W2 strain of P. falciparum. The most active compounds were also active against the atovaquone-resistant P. falciparum FCR3 strain and S. cerevisiae. Our study suggests the validity of the yeast bc1 complex structure as a model for the discovery of new antimalarial hits.