Oxidation shuts down an auto-inhibitory mechanism of von Willebrand factor

The blood protein von Willebrand factor (VWF) is a key link between inflammation and pathological thrombus formation. In particular, oxidation of methionine residues in specific domains of VWF due to the release of oxidants in inflammatory conditions has been linked to an increased platelet-binding activity. However, the atomistic details of how methionine oxidation activates VWF have not been elucidated to date. Yet understanding the activation mechanism of VWF under oxidizing conditions can lead to the development of novel therapeutics that target VWF selectively under inflammatory conditions in order to reduce its thrombotic activity while maintaining its haemostatic function. In this manuscript, we used a combination of a dynamic flow assay and molecular dynamics (MD) simulations to investigate how methionine oxidation removes an auto-inhibitory mechanism of VWF. Results from the dynamic flow assay revealed that oxidation does not directly activate the A1 domain, which is the domain in VWF that contains the binding site to the platelet surface receptor glycoprotein Ibα (GpIbα), but rather removes the inhibitory function of the neighboring A2 and A3 domains. Furthermore, the MD simulations combined with free energy perturbation calculations suggested that methionine oxidation may destabilize the binding interface between the A1 and A2 domains leading to unmasking of the GpIbα-binding site in the A1 domain.