Single Particle Tracking of ADAMTS13 (A Disintegrin and Metalloprotease with Thrombospondin Type-1 Repeats) Molecules on Endothelial von Willebrand Factor Strings

Abstract

Background: ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type-1 repeats) cleaves pro-thrombotic ultra-large von Willebrand factor (VWF) strings. Results: Customized single particle tracking enabled visualization of single ADAMTS13 enzymes that bind to long plateletdecorated VWF strings. Conclusion: ADAMTS13 readily bind to multiple available sites on VWF strings. Significance: Single molecule imaging can be used to study interactions between enzymes and large biopolymers in flow.

An Integrative Structural Biology Analysis of Von Willebrand Factor Binding and Processing by ADAMTS-13 in Solution

“…This latency explains the long half-life of ADAMTS-13 of up to a week in the circulation [24]. The M domain contains the characteristic zinc-binding consensus motif of metzincin MPs (H 224 -E-X-X-H-X-X-G-X-X-H 234 ) for metal binding and catalysis [25], and mutation of the general base glutamate to glutamine (E 225 Q) renders the enzyme incapable of cleaving vWF [26]. The M domain is followed by a disintegrin-like domain (D; G 294 -P 379 ), a thrombospondin-type 1 repeat (T; I 380 -E 439 ), a cysteine-rich domain (C; K 440 -C 555 ), a spacer domain (S; S 556 -P 682 ), a further seven T-like repeats, and two C-terminal CUB domains [23,27,28].…”

“…Notably, the crystal structure of isolated A2 reveals a globular domain in which the cleavage site is not accessible [30]. Indeed, turbulent flow in the bloodstream and shear stress during vWF string-mediated binding and agglutination of platelets triggers unfolding of A2 to expose the scissile bond [26,31,32]. Remarkably, the interaction between A2 and ADAMTS-13 exceeds the M domain because the minimal length of a vWF-derived fragment that mimics the unfolded state of A2 and is cleaved spans 73 residues (D1596-R1668 ; vWF-peptide, see [33]).…”