Which amino acid is carboxylated in carboxylation of clotting factors by Vitamin K?

Vitamin K is required for the post translational carboxylation of glutamic acid, which is necessary for calcium binding to -carboxylated proteins such as prothrombin (factor II); factors VII, IX, and X; protein C; protein S; and proteins found in bone (osteocalcin) and vascular smooth muscle (e.g., matrix Gla protein). Warfarin-type drugs inhibit -carboxylation by preventing the conversion of vitamin K to its active hydroquinone form. Must know: There are two natural forms of vitamin K: vitamin K1, also known as phylloquinone, from vegetable and animal sources, and vitamin K2, or menaquinone, which is synthesized by bacterial flora and found in hepatic tissue. Ref: Russell R.M., Suter P.M. (2012). Chapter 74. Vitamin and Trace Mineral Deficiency and Excess. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.