Effect of the warfarin-resistant VKOR mutant on FIXgla-PC carboxylation. (A) The warfarin-resistant VKOR-Y139F mutant was transiently expressed in HEK293 (■) and AV12 cells (). Thirty hours after transfection, cells were cultured in medium containing 5μM KO and 2μM warfarin for 48 hours. The concentration of carboxylated FIXgla-PC in the medium was measured by ELISA. The control was the cell line transfected with empty vector, representing endogenous VKOR. (B) AV12 cells (■) or AV12 cells that were stably expressing the warfarin-resistant VKOR-Y139F mutant () were cultured in medium containing 5μM KO (KO) or 5μM KO + 2μM warfarin (KO + W) for 48 hours. The concentration of carboxylated FIXgla-PC in the medium was measured by ELISA.