The organic component of the bone matrix comprises 40% dry weight of bone. The organic
component is mostly composed of type I collagen and small amounts of non-collagenous proteins
(NCPs) (10-15% of the total bone protein content). The small integrin-binding ligand N-linked glycoprotein
(SIBLING) family, a NCP, is considered to play a key role in bone mineralization. SIBLING
family of proteins share common structural features and includes the arginine-glycine-aspartic acid
(RGD) motif and acidic serine- and aspartic acid-rich motif (ASARM). Clinical manifestations of gene
mutations and/or genetically modified mice indicate that SIBLINGs play diverse roles in bone and extraskeletal
tissues. ASARM peptides might not be primary responsible for the functional diversity of SIBLINGs, but this
motif is suggested to be a key domain of SIBLINGs. However, the exact function of ASARM peptides is poorly understood.
In this article, we discuss the considerable progress made in understanding the role of ASARM as a bioactive peptide.
Keywords: Acidic serine- and aspartic acid-rich motif (ASARM), bone mineralization, matrix extracellular phosphoglycoprotein
(MEPE), small integrin-binding ligand N-linked glycoprotein (SIBLING).
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