Computational study of the mechanism of binding of antifungal icofungipen in the active site of eukaryotic isoleucyl tRNA synthetase from Candida albicans.

Abstract

The eukaryotic fungal species Candida albicans is a critical infective pathogenic agent. The β-amino acid, Icofungipen, is an effective inhibitor of Candida albicans. Icofungipen binds at the active site of the isoleucyl tRNA synthetase (IleRS) from Candida albicans (^CaIleRS) and halts protein translation in fungus. In the present work, we have investigated the mechanism of binding of Icogungipen (abbreviated as IFP). Molecular dynamics (MD) simulations show that the carboxylic acid group of IFP in the ^CaIleRS: IFP complex is more oriented towards the Connective Polypeptide (CP) core loop compared to the carboxylic acid group of Ile in the ^CaIleRS: Ile complex. The Arg 410 of the CP core loop near the substrate is extended towards the IFP. Due to the difference in the conformation of residues of the CP core loop, the KMSKR loop is more proximal to the CP core loop in ^CaIleRS: IFP. The editing domain which is covalently linked with the CP core loop in the ^CaIleRS: IFP complex is also oriented in such a way that the active site cavity is narrow and longer. The metadynamics calculation shows that the IFP is trapped in a deeper potential well compared to Ile which is due to the effective closure of the gateway of the active site by KMSKR and CP core loop. The thin, long shape of the active site and the closed gate of the active site in ^CaIleRS: IFP complex is responsible for the effective capture of IFP relative to Ile in the active site.