Figure 1.

Functional study of GGCX in HEK293 cells using different VKD reporter proteins. (A) Diagram of structurally distinct VKD reporter proteins. Gla residues are indicated by γ. (B) Carboxylation of the 3 VKD reporter proteins in HEK293 cells in response to vitamin K. Wild-type GGCX was transiently expressed in GGCX-deficient HEK293 cells stably expressing FIXgla-PC, MGP, or BGP. Transfected cells were incubated with increasing concentrations of vitamin K for 48 hours. The carboxylation efficiency of the reporter protein was determined in the cell culture medium by ELISA. (C) Half-maximal stimulation concentrations of vitamin K (EC₅₀) (obtained by nonlinear regression using GraphPad Prism 8.0) for the carboxylation of BGP, MGP, and FIXgla-PC. Data are presented as means ± standard deviation (SD).