Subunit Flexibility of Multimeric von Willebrand Factor/Factor VIII Complexes.

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Background:

• Von Willebrand factor (VWF) is a large glycoprotein complex crucial for primary hemostasis.
• VWF mediates platelet adhesion and aggregation and carries coagulation factor VIII.
• Plasma VWF exists as heterogeneous multimers composed of disulfide-linked subunits.

Purpose of the Study:

• To characterize the structural conformation and flexibility of plasma-derived human VWF/fVIII complexes.
• To determine the relationship between molecular weight and hydrodynamic properties of VWF multimers.
• To investigate the flexibility of VWF subunits and their domain interactions.

Main Methods:

• Size-exclusion chromatography for fractionation of VWF/fVIII complexes.
• Sodium dodecyl sulfate agarose gel electrophoresis for multimer analysis.
• Sedimentation velocity analytical ultracentrifugation (SV AUC), dynamic light scattering (DLS), and multi-angle light scattering (MALS) for molecular characterization.

Main Results:

• Weight-average molecular weights (Mw) were measured using MALS and SV AUC/DLS.
• Analysis of Mark-Houwink-Kuhn-Sakurada exponents indicated a random coil conformation for VWF multimers.
• Ratios of radius of gyration to hydrodynamic radius were consistent with a highly flexible VWF structure.

Conclusions:

• VWF multimers adopt a flexible, random coil conformation in solution.
• The data suggest a contour length significantly greater than the persistence length, indicating high domain flexibility.
• These findings provide insights into the structural dynamics of VWF essential for its function in hemostasis.