Noncollagenous proteins bone matrix

A key to the development of osteoblasts appears to be an osteoblast-specific transcription factor OS/2 or Cbfal.693-695 Mutations in human Cbfal are linked to a series of skeletal defects.696 A unique change accompanying conversion of a precursor cell into an osteoblast is the formation of a 49-residue y-carboxyglutamate (Gla)-containing protein called osteocalcin.697 (See also Box 15-F). It is the most abundant noncollagenous protein of bone. Its three Gla residues doubtless help to bind calcium ions and osteocalcin may be an initiator of crystallization. Osteocalcin has also been found in fish scales.698 Also present in bone is a 74-residue matrix Gla protein which has 5 Gla residues.699... 

It is the most abundant of the noncollagen proteins of bone matrix, accounting for 1% to 2% of total bone protein, or 15% of noncollagen bone protein. Osteocalcin synthesis is induced by physiological concenUations of calcitriol, and the release of osteocalcin into the circulation provides a sensitive marker of vitamin D action and metabolic bone disease (Section 3.5). 

Osteocalcin Major noncollagen protein of bone matrix... 

Boskey AL (1989) Noncollagenous matrix proteins and their role in mineralization. Bone Miner 6,111-123. 

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