Cryo-EM structure of the A₂B₂ heterotetramer of FXIII showing the arrangement of the 2 A subunits, with the 4 constitutive domains and the 2 B subunits containing Sushi domains 1 and 2 visible in the high-resolution (2.4-Å) structure. Note the highly symmetric assembly with the B subunits bridging the core domains of the A subunits.