A Vitamin K-dependent protein (VKDP) is a protein that can bind calcium ions but only after being carboxylated at a certain glutamic residue.
This carboxylation, said to activate the protein, is facilitated by some form of vitamin K1 or vitamin K2.
The relevant part of a vitamin K-dependent protein is a Gla domain, and such a protein is informally called a Gla protein.
[1] Some Gla proteins have "Gla" in their name, for example Matrix Gla protein,[1] but many don't, such as osteocalcin.
[2] This protein-related article is a stub.