TY  - JOUR
A1  - Posch, Sandra
A1  - Aponte-Santamaria, Camilo Andrés
A1  - Schwarzl, Richard
A1  - Karner, Andreas
A1  - Radtke, Matthias
A1  - Gräter, Frauke
A1  - Obser, Tobias
A1  - König, Gesa
A1  - Brehm, Maria Alexandra
A1  - Gruber, Hermann J.
A1  - Netz, Roland R.
A1  - Baldauf, Carsten
A1  - Schneppenheim, Reinhard
A1  - Tampé, Robert
A1  - Hinterdorfer, Peter
T1  - Mutual a domain interactions in the force sensing protein von Willebrand factor
T2  - Journal of structural biology
N2  - The von Willebrand factor (VWF) is a glycoprotein in the blood that plays a central role in hemostasis. Among other functions, VWF is responsible for platelet adhesion at sites of injury via its A1 domain. Its adjacent VWF domain A2 exposes a cleavage site under shear to degrade long VWF fibers in order to prevent thrombosis. Recently, it has been shown that VWF A1/A2 interactions inhibit the binding of platelets to VWF domain A1 in a force-dependent manner prior to A2 cleavage. However, whether and how this interaction also takes place in longer VWF fragments as well as the strength of this interaction in the light of typical elongation forces imposed by the shear flow of blood remained elusive. Here, we addressed these questions by using single molecule force spectroscopy (SMFS), Brownian dynamics (BD), and molecular dynamics (MD) simulations. Our SMFS measurements demonstrate that the A2 domain has the ability to bind not only to single A1 domains but also to VWF A1A2 fragments. SMFS experiments of a mutant [A2] domain, containing a disulfide bond which stabilizes the domain against unfolding, enhanced A1 binding. This observation suggests that the mutant adopts a more stable conformation for binding to A1. We found intermolecular A1/A2 interactions to be preferred over intramolecular A1/A2 interactions. Our data are also consistent with the existence of two cooperatively acting binding sites for A2 in the A1 domain. Our SMFS measurements revealed a slip-bond behavior for the A1/A2 interaction and their lifetimes were estimated for forces acting on VWF multimers at physiological shear rates using BD simulations. Complementary fitting of AFM rupture forces in the MD simulation range adequately reproduced the force response of the A1/A2 complex spanning a wide range of loading rates. In conclusion, we here characterized the auto-inhibitory mechanism of the intramolecular A1/A2 bond as a shear dependent safeguard of VWF, which prevents the interaction of VWF with platelets.
KW  - Atomic force microscopy
KW  - Single molecule force spectroscopy
KW  - Molecular dynamics simulation
KW  - Brownian dynamics simulation
KW  - von Willebrand factor
KW  - Primary hemostasis
Y1  - 2017
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/44261
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-442616
SN  - 1095-8657
SN  - 1047-8477
N1  - © 2016 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
VL  - 197
IS  - 1
SP  - 57
EP  - 64
PB  - Elsevier
CY  - San Diego, Calif.
ER  -