Protein S is named for Seattle, Washington, where it was originally discovered and purified[7] by Earl Davie's group in 1977.

The Gla and EGF-like domains stay connected after the cleavage by a disulfide bond.

Protein S binds to the negatively charged phospholipids and functions as a bridge between the apoptotic cell and the phagocyte.

This bridging expedites phagocytosis and allows the cell to be removed without giving rise to inflammation or other signs of tissue damage.

Protein S does not bind to the nascent complement complex C5,6,7 to prevents it from inserting into a membrane.