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

The eukaryotic fungal species Candida albicans is a critical infective pathogenic agent. The ß-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.Communicated by Ramaswamy H. Sarma.

Amino Acid Metabolism and Transport Mechanisms as Potential Antifungal Targets.

Discovering new drugs for treatment of invasive fungal infections is an enduring challenge. There are only three major classes of antifungal agents, and no new class has been introduced into clinical practice in more than a decade. However, recent advances in our understanding of the fungal life cycle, functional genomics, proteomics, and gene mapping have enabled the identification of new drug targets to treat these potentially deadly infections. In this paper, we examine amino acid transport mechanisms and metabolism as potential drug targets to treat invasive fungal infections, including pathogenic yeasts, such as species of Candida and Cryptococcus, as well as molds, such as Aspergillus fumigatus. We also explore the mechanisms by which amino acids may be exploited to identify novel drug targets and review potential hurdles to bringing this approach into clinical practice.

Stereo- and Regiocontrolled Syntheses of Exomethylenic Cyclohexane ß-Amino Acid Derivatives.

Cyclohexane analogues of the antifungal icofungipen [(1R,2S)-2-amino-4-methylenecyclopentanecarboxylic acid] were selectively synthesized from unsaturated bicyclic ß-lactams by transformation of the ring olefinic bond through three different regio- and stereocontrolled hydroxylation techniques, followed by hydroxy group oxidation and oxo-methylene interconversion with a phosphorane. Starting from an enantiomerically pure bicyclic ß-lactam obtained by enzymatic resolution of the racemic compound, an enantiodivergent procedure led to the preparation of both dextro- and levorotatory cyclohexane analogues of icofungipen.