Characterization of the GGCX knockout reporter cells. (A) Immunoblotting of wild-type (lane 1) and GGCX knockout (lane 2) HEK293 cells. Endogenous GGCX band is indicated by the arrow. (B) Carboxylation activity of GGCX-knockout cells (GGCX-KO) and the cells transfected with wild-type GGCX.