title: Intermolecular interactions and characterization of the novel factor Xa exosite involved in macromolecular recognition and inhibition: crystal structure of human Gla-domainless factor Xa complexed with the anticoagulant protein NAPc2 from the hematophagous nematode Ancylostoma caninum.
abstract: NAPc2, an anticoagulant protein from the hematophagous nematode Ancylostoma caninum evaluated in phase-II/IIa clinical trials, inhibits the extrinsic blood coagulation pathway by a two step mechanism, initially interacting with the hitherto uncharacterized factor Xa exosite involved in macromolecular recognition and subsequently inhibiting factor VIIa (K(i)=8.4 pM) of the factor VIIa/tissue factor complex. NAPc2 is highly flexible, becoming partially ordered and undergoing significant structural changes in the C terminus upon binding to the factor Xa exosite. In the crystal structure of the ternary factor Xa/NAPc2/selectide complex, the binding interface consists of an intermolecular antiparallel beta-sheet formed by the segment of the polypeptide chain consisting of residues 74-80 of NAPc2 with the residues 86-93 of factor Xa that is additional maintained by contacts between the short helical segment (residues 67-73) and a turn (residues 26-29) of NAPc2 with the short C-terminal helix of factor Xa (residues 233-243). This exosite is physiologically highly relevant for the recognition and inhibition of factor X/Xa by macromolecular substrates and provides a structural motif for the development of a new class of inhibitors for the treatment of deep vein thrombosis and angioplasty.
authors.affiliation: Department of Physics, IBILCE/UNESP, São José do Rio Preto, SP 15054-000, Brazil.
authors.forename: M T
authors.initials: MT
authors.lastname: Murakami
authors.forename: J
authors.initials: J
authors.lastname: Rios-Steiner
authors.forename: S E
authors.initials: SE
authors.lastname: Weaver
authors.forename: A
authors.initials: A
authors.lastname: Tulinsky
authors.forename: J H
authors.initials: JH
authors.lastname: Geiger
authors.forename: R K
authors.initials: RK
authors.lastname: Arni
mesh_terms: D000722:Ancylostoma / Q000737:chemistry*; D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology; D001665:Binding Sites; D002417:Cattle; D015942:Factor VIIa / Q000737:chemistry / Q000378:metabolism; D015951:Factor Xa / Q000737:chemistry* / Q000378:metabolism; D015801:Helminth Proteins / Q000737:chemistry*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D013925:Thromboplastin / Q000737:chemistry / Q000378:metabolism
chemical_list: D000925:Anticoagulants; D015801:Helminth Proteins; C400226:anti-coagulant protein C2, Ancylostoma caninum; D013925:Thromboplastin; D015942:Factor VIIa; D015951:Factor Xa