How Does Osteocalcin Lacking γ-Glutamic Groups Affect Biomimetic Apatite Formation and What Can We Say About Its Structure in Mineral-Bound Form?

•Bone mimetic apatite was crystallized with osteocalcin lacking γ-carboxylates.•Unmodified OC induces formation of highly ordered hydroxyapatite crystals.•Unmodified OC minimizes the formation of an amorphous phase on the crystallites.•Contacts between protein carbons and phosphates in the mineral were not found.•Apatite bound osteocalcin is in helix bundle form, like the free carboxylated form.