Coexpression of E30Q mutant with WT PZ. (A) WT PZ expression vector (10 μg) was cotransfected to BHK cells with varying amounts of the E30Q expression vector. Forty-eight hours after transfection, cells were treated with vitamin K for 24 hours. PZ in the medium was collected by barium-citrate absorption because of the low levels of PZ expressed by transient transfection. (B) The E30Q expression plasmid was transfected to the BHK cells stably expressing WT PZ.