期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：23
页码：9226-9231
DOI：10.1073/pnas.0903679106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The lengths of von Willebrand factor (VWF) concatamers correlate with hemostatic potency. After secretion in plasma, length is regulated by hydrodynamic shear force-dependent unfolding of the A2 domain, which is then cleaved by a specific protease. The 1.9-A crystal structure of the A2 domain demonstrates evolutionary adaptations to this shear sensor function. Unique among VWF A (VWA) domains, A2 contains a loop in place of the {alpha}4 helix, and a cis-proline. The central {beta}4-strand is poorly packed, with multiple side-chain rotamers. The Tyr-Met cleavage site is buried in the {beta}4-strand in the central hydrophobic core, and the Tyr structurally links to the C-terminal {alpha}6-helix. The {alpha}6-helix ends in 2 Cys residues that are linked by an unusual vicinal disulfide bond that is buried in a hydrophobic pocket. These features may narrow the force range over which unfolding occurs and may also slow refolding. Von Willebrand disease mutations, which presumably lower the force at which A2 unfolds, are illuminated by the structure.
