title: Conformation of a novel tetrapeptide inhibitor NH2-D-Trp-D-Met-Phe(pCl)-Gla-NH2 bound to farnesyl-protein transferase.
abstract: Farnesyl-protein transferase (FPTase) catalyzes the posttranslational farnesylation of the cysteine residue located in the C-terminal tetrapeptide of the Ras oncoprotein. Prenylation of this residue is essential for membrane association and cell-transforming activities of ras. Inhibitors of FPTase have been demonstrated to display antitumor activity in both tissue culture and animal models, and thus represent a potential therapeutic strategy for the treatment of human cancers. A synthetic tetrapeptide library, which included an expanded set of 68 L-, D- and noncoded amino acids, has been screened for inhibitors of FPTase activity. The tetrapeptide, NH2-D-Trp-D-Met-L-Phe(pCl)-L-Gla-NH2 was shown to be competitive with the isoprenyl cosubstrate, farnesyl diphosphate (FPP) but not with the peptide substrate, the C-terminal tetrapeptide of the Ras protein. The FPTase-bound conformation of the inhibitor, NH2-D-Trp-D-Met-L-Phe(pCl)-L-Gla-NH2 was determined by NMR spectroscopy. Distance constraints were derived from two-dimensional transferred nuclear Overhauser effect (TRNOE) experiments. Ligand competition experiments identified the NOEs that originate from the active-site conformation of the inhibitor. Structures were calculated using a combination of distance geometry and restrained energy minimization. The peptide backbone is shown to adopt a reverse-turn conformation most closely approximating a type II' beta-turn. The resolved conformation of the inhibitor represents a distinctly different structural motif from that determined for Ras-competitive inhibitors. Knowledge of the bound conformation of this novel inhibitor provides a template and future direction for the design of new classes of FPTase antagonists.
authors.affiliation: Department of Medicinal Chemistry, Merck Research Laboratories, West Point, PA 19486, USA. michael_bogusky@merck.com
authors.forename: M J
authors.initials: MJ
authors.lastname: Bogusky
authors.forename: J C
authors.initials: JC
authors.lastname: Culberson
authors.forename: S M
authors.initials: SM
authors.lastname: Pitzenberger
authors.forename: V M
authors.initials: VM
authors.lastname: Garsky
authors.forename: A
authors.initials: A
authors.lastname: Wallace
authors.forename: A
authors.initials: A
authors.lastname: Pessi
authors.forename: K S
authors.initials: KS
authors.lastname: Koblan
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009842:Oligopeptides / Q000737:chemistry* / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D009842:Oligopeptides; C121353:tryptophyl-methionyl-4-chlorophenylalanyl-gamma-carboxyglutamamide; D019883:Alkyl and Aryl Transferases; C064911:p21(ras) farnesyl-protein transferase