NMR-STUDIES OF NOVEL INHIBITORS BOUND TO FARNESYL-PROTEIN TRANSFERASE

Farnesyl-protein transferase (FPTase) catalyzes the posttranslational farnesylation of the cysteine residue located in the carboxyl-terminal tetrapeptide of the Ras oncoprotein. Prenylation of this residue is e ssential for the membrane association and cell-transforming activities of ras. Inhibitors of FPTase have been demonstrated to inhibit ras-de pendent cell transformation and thus represent a potential therapeutic strategy for the treatment of human cancers. The FPTase-bound conform ation of a tetrapeptide inhibitor, CVWM, and a novel pseudopeptide inh ibitor, L-739,787, have been determined by NMR spectroscopy. Distance constraints were derived from two-dimensional transferred nuclear Over hauser effect experiments. Ligand competition experiments identified t he NOEs that originate from the active-site conformation. Structures w ere calculated with the combination of distance geometry and restraine d energy minimization. Both peptide backbones are shown to adopt nonid eal reverse-turn conformations most closely approximating a type III b eta-turn. These results provide a basis for understanding the spatial arrangements necessary for inhibitor binding and selectivity and may a id in the design of therapeutic agents.