A novel mechanism underlying allosteric regulation of ADAMTS-13 revealed by hydrogen-deuterium exchange plus mass spectrometry.

BACKGROUND: ADAMTS-13, a plasma metalloprotease, cleaves von Willebrand factor. ADAMTS-13 activity appears to be regulated through allosteric inhibition by its distal C-terminus.

OBJECTIVES: The objective of this study was to better understand how domain-domain interactions may affect ADAMTS-13 conformations and functions.

METHODS: We performed deuterium-hydrogen exchange plus mass spectrometry to assess the number and rate of deuterium incorporation into various peptides of full-length ADAMTS-13 and its truncated variants.

RESULTS: Under physiological conditions, a bimodal distribution of deuterium incorporation was detected in the peptides from metalloprotease (217-230 and 282-304), cysteine-rich (446-482), and CUB (for complement C1r/C1s, Uegf, Bmp1) domains (1185-1214, 1313-1330, 1341-1347, 1358-1378, and 1393-1407) of full-length recombinant ADAMTS-13, but not of truncated variants. These results suggest that the full-length ADAMTS-13 undergoes conformational changes. On removal of the middle and distal C-terminal domains, the number and rate of deuterium incorporation were increased in the peptides from cysteine-rich (445-467, 467-482, and 495-503) and spacer domains (621-642 and 655-654) but decreased in the peptides from metalloprotease (115-124, 217-230, and 274-281). Moreover, most peptides, except for 217-230 and 1357-1376, exhibited a pD-dependent deuterium incorporation in the full-length ADAMTS-13, but not in the truncated variant (eg, MDTCS or T5C). These results further suggest that the bimodal deuterium incorporation observed in the peptides from the full-length ADAMTS-13 is the result of potential impact from the middle to distal C-terminal domains. Surface plasmon resonance revealed the direct binding interactions between the distal and proximal domains of ADAMTS-13.

CONCLUSION: Our results provide novel insight on how intramolecular interactions may affect conformations of ADAMTS-13, thus regulating its proteolytic functions.