SpeciFlex: A Protocol for Mining Binding Site Conformational Selectivity in Structure-Based Inhibitor Discovery

Selectivity for a target site is challenging when the site is conserved in homologous proteins. A novel protocol is presented for attaining selectivity by taking advantage of conformational population differences between homologs. Conformational ensembles of the targeted protein and the homolog are compared to identify pockets significantly populated in the target, but rarely or never sampled in the homolog. SLIDE screening then identifies molecules that fit the unique pocket and also interact well with an adjacent substrate pocket. The SpeciFlex protocol, demonstrated for a pair of pyrophosphokinases, yields ligand candidates with good interactions in both the substrate and unique pockets of the target Yersinia pestis protein, while selecting against interactions with the homologous site in Escherichia coli.