title: Dimeric Organization of Blood Coagulation Factor VIII bound to Lipid Nanotubes.
abstract: Membrane-bound Factor VIII (FVIII) has a critical function in blood coagulation as the pro-cofactor to the serine-protease Factor IXa (FIXa) in the FVIIIa-FIXa complex assembled on the activated platelet membrane. Defects or deficiency of FVIII cause Hemophilia A, a mild to severe bleeding disorder. Despite existing crystal structures for FVIII, its membrane-bound organization has not been resolved. Here we present the dimeric FVIII membrane-bound structure when bound to lipid nanotubes, as determined by cryo-electron microscopy. By combining the structural information obtained from helical reconstruction and single particle subtomogram averaging at intermediate resolution (15-20 Å), we show unambiguously that FVIII forms dimers on lipid nanotubes. We also demonstrate that the organization of the FVIII membrane-bound domains is consistently different from the crystal structure in solution. The presented results are a critical step towards understanding the mechanism of the FVIIIa-FIXa complex assembly on the activated platelet surface in the propagation phase of blood coagulation.
authors.affiliation: Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555, USA.
authors.forename: Daniela
authors.initials: D
authors.lastname: Dalm
authors.affiliation: 1] Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA [2] National Center for Macromolecular Imaging, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Jesus G
authors.initials: JG
authors.lastname: Galaz-Montoya
authors.affiliation: Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555, USA.
authors.forename: Jaimy L
authors.initials: JL
authors.lastname: Miller
authors.affiliation: Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555, USA.
authors.forename: Kirill
authors.initials: K
authors.lastname: Grushin
authors.affiliation: School of Medicine, University of Texas Medical Branch, Galveston, TX 77555, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Villalobos
authors.affiliation: Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX 77555, USA.
authors.forename: Alexey Y
authors.initials: AY
authors.lastname: Koyfman
authors.affiliation: 1] Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA [2] National Center for Macromolecular Imaging, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Schmid
authors.affiliation: 1] Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555, USA [2] Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA.
authors.forename: Svetla
authors.initials: S
authors.lastname: Stoilova-McPhie
mesh_terms: D000818:Animals; D020285:Cryoelectron Microscopy; D005169:Factor VIII / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D008055:Lipids / Q000737:chemistry; D008958:Models, Molecular; D043942:Nanotubes / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization; D014054:Tomography / Q000379:methods
chemical_list: D008055:Lipids; D005169:Factor VIII