Plasma Kallikrein Structure Reveals Apple Domain Disc Rotated Conformation Compared to Factor XI.

Essentials Zymogen PK is activated to PKa and cleaves substrates kininogen and FXII contributing to bradykinin generation. Monomeric PKa and dimeric homologue FXI utilize the N‐terminal apple domains to recruit substrates. A high‐resolution 1.3 A structure of full‐length PKa reveals an active conformation of the protease and apple domains. The PKa protease and four‐apple domain disc organization is 180° rotated compared to FXI.