Poly(ADP-ribose) binding sites on collagen I fibrils for nucleating intrafibrillar bone mineral.

Bone calcification is essential for vertebrate life. The mechanism by which mineral ions are transported into collagen fibrils to induce intrafibrillar mineral formation requires a calcium binding biopolymer that also has highly selective binding to the collagen fibril hole zones where intrafibrillar calcification begins, over other bone extracellular matrix components. Poly(ADP-ribose) (PAR) has been shown to be a candidate biopolymer for this process and we show here that PAR has high affinity, highly conserved binding sites in the collagen type I C-terminal telopeptides. The identification of these PAR-collagen binding sites gives insights into the chemical mechanisms underlying bone calcification and possible mechanisms behind pathologies where there is dysfunctional bone calcification.