The γ-carboxylation recognition sites of known vitamin K-dependent proteins. The propeptides of the vitamin K-dependent blood coagulation proteins contain a γ-carboxylation recognition site that directs carboxylation.8 A phenylalanine at position −16 and an alanine at position −10 are well conserved within the propeptides of carboxylase substrates, as are aliphatic hydrophobic residues (isoleucine, leucine, and valine) at position −17 and −15. Recent data suggest that, whereas phenylalanine at −16 is preferred, leucine, valine, and lysine at this position can also support carboxylation.31