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: M T Murakami, J Rios-Steiner, S E Weaver, A Tulinsky, J H Geiger, R K Arni
• Journal: Journal of molecular biology (J Mol Biol) Vol. 366 Issue 2 Pg. 602-10 (Feb 16 2007) ISSN: 0022-2836 [Print] Netherlands
• PMID: 17173931 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Anticoagulants
• Helminth Proteins
• anti-coagulant protein C2, Ancylostoma caninum
• Thromboplastin
• Factor VIIa
• Factor Xa

Topics

• Ancylostoma (chemistry)
• Animals
• Anticoagulants (pharmacology)
• Binding Sites
• Cattle
• Factor VIIa (chemistry, metabolism)
• Factor Xa (chemistry, metabolism)
• Helminth Proteins (chemistry)
• Humans
• Models, Molecular
• Molecular Sequence Data
• Protein Binding
• Protein Structure, Tertiary
• Structure-Activity Relationship
• Thromboplastin (chemistry, metabolism)