Recombinant expression of the His224 variant in HEK-EBNA cells. Supernatant of HEK-EBNA cells transfected with the human SERPINC1 Asn224 (residue present in the wild-type molecule) or the mutant His224 cDNAs in the wild-type (Ser169) or β (Ala169) backgrounds were analyzed by Western blotting. The number of N-glycans of each form is indicated. The formation of T-AT, when incubated with thrombin (T) with or without UFH, is pointed by arrows. Cleaved antithrombin (cAT) is also indicated.