PMID: 25604127

Authors:

Pathak M, Wilmann P, Awford J, Li C, Fischer PM, Dreveny I, Dekker LV, Emsley J

Title:

Coagulation Factor XII protease domain crystal structure.

Journal:

J Thromb Haemost. 2015 Jan 20. doi: 10.1111/jth.12849.

Abstract:

BACKGROUND: Coagulation factor XII (FXII) is a serine protease important to kinin generation and blood coagulation cleaving substrates plasma kallikrein and factor XI (FXI). OBJECTIVE: To investigate FXII zymogen activation and substrate recognition we determined the crystal structure of the FXII protease domain. METHODS AND RESULTS: A series of recombinant FXII protease constructs were characterized measuring cleavage of chromogenic peptide and plasma kallikrein protein substrates. This revealed that the FXII protease construct spanning the light chain has unexpectedly weak proteolytic activity compared to beta-FXIIa which has an additional 9 amino acid remnant of the heavy chain present. Consistent with this data the crystal structure of the light chain protease reveals a zymogen conformation for active site residues Gly193 and Ser195 where the oxyanion hole is absent. The Asp194 side chain salt bridges to Arg73 is an atypical conformation of the 70-loop. In one crystal form the S1 pocket loops are partially flexible which is typical of a zymogen. In a second crystal form of the deglycosylated light chain the S1 pocket loops are ordered and a short alpha-helix in the 180-loop of the structure results in an enlarged and distorted S1 pocket with a buried conformation of residue Asp189 critical for P1 Arg substrate recognition. The FXII structures defines patches of negative charge surrounding the active site cleft which may be critical for interactions with inhibitors and substrates. CONCLUSIONS: This data provides the first structural scaffold for understanding FXII substrate recognition and zymogen activation. This article is protected by copyright. All rights reserved.