title: Extensive small-angle X-ray scattering studies of blood coagulation factor VIIa reveal interdomain flexibility.
abstract: Blood coagulation factor VIIa (FVIIa) is used in the treatment of replacement therapy resistant hemophilia patients, and FVIIa is normally activated upon complex formation with tissue factor (TF), potentially in context with structural rearrangements. The solution behavior of uncomplexed FVIIa is important for understanding the mechanism of activation and for the stability and activity of the pharmaceutical product. However, crystal structures of FVIIa in complex with TF and of truncated free FVIIa reveal different overall conformations while previous small-angle scattering studies suggest FVIIa always to be fully extended in solution. Here, small-angle X-ray scattering analysis of multiple forms of FVIIa and TF under several experimental conditions elaborate extensively on the understanding of the solution behavior of FVIIa. We reveal significant FVIIa domain flexibility in solution, whereas TF has a well-defined conformation. Unspecific formation of dimers of FVIIa is also observed and varies with experimental conditions. In particular, active site-inhibited FVIIa displays a distinct solution behavior different from that of uninhibited FVIIa, which may reflect structural rearrangements causing resistance to activation, thereby emphasizing the connection between the distribution of different conformations of FVII and the mechanism of activation.
authors.affiliation: Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark. chrp@farma.ku.dk
authors.forename: Charlotte Rode
authors.initials: CR
authors.lastname: Mosbaek
authors.forename: David
authors.initials: D
authors.lastname: Nolan
authors.forename: Egon
authors.initials: E
authors.lastname: Persson
authors.forename: Dmitri I
authors.initials: DI
authors.lastname: Svergun
authors.forename: Jens Thostrup
authors.initials: JT
authors.lastname: Bukrinsky
authors.forename: Bente
authors.initials: B
authors.lastname: Vestergaard
mesh_terms: D003460:Crystallization; D015942:Factor VIIa / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D022142:Secretory Vesicles / Q000737:chemistry / Q000378:metabolism; D013925:Thromboplastin / Q000737:chemistry / Q000378:metabolism; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D013925:Thromboplastin; D015942:Factor VIIa