title: Warfarin and vitamin K compete for binding to Phe55 in human VKOR.
abstract: Vitamin K epoxide reductase (VKOR) catalyzes the reduction of vitamin K quinone and vitamin K 2,3-epoxide, a process essential to sustain γ-carboxylation of vitamin K-dependent proteins. VKOR is also a therapeutic target of warfarin, a treatment for thrombotic disorders. However, the structural and functional basis of vitamin K reduction and the antagonism of warfarin inhibition remain elusive. Here, we identified putative binding sites of both K vitamers and warfarin on human VKOR. The predicted warfarin-binding site was verified by shifted dose-response curves of specified mutated residues. We used CRISPR-Cas9-engineered HEK 293T cells to assess the vitamin K quinone and vitamin K 2,3-epoxide reductase activities of VKOR variants to characterize the vitamin K naphthoquinone head- and isoprenoid side chain-binding regions. Our results challenge the prevailing concept of noncompetitive warfarin inhibition because K vitamers and warfarin share binding sites on VKOR that include Phe55, a key residue binding either the substrate or inhibitor.
authors.affiliation: Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany.
authors.forename: Katrin J
authors.initials: KJ
authors.lastname: Czogalla
authors.affiliation: Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany.
authors.forename: Arijit
authors.initials: A
authors.lastname: Biswas
authors.affiliation: Institute of Molecular Medicine, University Hospital Bonn, Bonn, Germany.
authors.forename: Klara
authors.initials: K
authors.lastname: Höning
authors.affiliation: Institute of Molecular Medicine, University Hospital Bonn, Bonn, Germany.|Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, Munich, Germany.
authors.forename: Veit
authors.initials: V
authors.lastname: Hornung
authors.affiliation: Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Liphardt
authors.affiliation: Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany.|Center for Rare Diseases Bonn (ZSEB), University Clinic Bonn, Bonn, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Watzka
authors.affiliation: Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany.|Center for Rare Diseases Bonn (ZSEB), University Clinic Bonn, Bonn, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Oldenburg
mesh_terms: D055162:Biocatalysis; D020134:Catalytic Domain; D004351:Drug Resistance; D057809:HEK293 Cells; D006801:Humans; D062105:Molecular Docking Simulation; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000737:chemistry; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical; D010837:Vitamin K 1 / Q000031:analogs & derivatives / Q000737:chemistry; D024482:Vitamin K 2 / Q000737:chemistry; D064417:Vitamin K Epoxide Reductases / Q000037:antagonists & inhibitors / Q000737:chemistry*; D014859:Warfarin / Q000737:chemistry*
chemical_list: D024482:Vitamin K 2; C016186:vitamin K1 oxide; D010649:Phenylalanine; D014859:Warfarin; D010837:Vitamin K 1; D064417:Vitamin K Epoxide Reductases