Characterization of a novel dentin matrix acidic phosphoprotein. Implications for induction of biomineralization

• Published in: The Journal of biological chemistry Vol. 268; no. 17; pp. 12624 - 12630
• Main Authors: GEORGE, A, SABSAY, B, SIMONIAN, P. A. L, VEIS, A
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 15-06-1993
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Animals; Base Sequence; Biological and medical sciences; Calcification, Physiologic; Cloning, Molecular; Dental Pulp - metabolism; DNA; Extracellular Matrix Proteins; Fundamental and applied biological sciences. Psychology; Gene Library; Incisor; Male; Miscellaneous; Molecular Sequence Data; Odontoblasts - metabolism; Oligodeoxyribonucleotides; Organ Culture Techniques; Organ Specificity; Phosphoproteins - biosynthesis; Phosphoproteins - isolation & purification; Polymerase Chain Reaction; Protein Conformation; Proteins; Rats; Rats, Sprague-Dawley; Restriction Mapping; RNA, Messenger - metabolism; Space life sciences; Dentin; Vertebrata; Mammalia; Rat; Phosphoproteins; Mineralization; Acidic protein; Rodentia; Primary structure; Molecular cloning; Gene expression
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(18)31434-0

Acidic phosphorylated proteins have been shown to be prominent constituents of the extracellular matrix of bone and dentin.
The acidic phosphoproteins of bone contain more glutamic acid than aspartic acid and a lower serine content than either. On
the other hand, the major dentin acidic phosphoproteins, phosphophoryns, have been defined as aspartic acid- and serine-rich
proteins, with a lesser content of glutamic acid. Both sets of phosphoproteins have been implicated as key participants in
regulating mineralization, but it has been difficult to unify their mechanisms of action. We have now identified, by cDNA
cloning, a new serine-rich acidic protein of the dentin matrix, AG1, with a composition intermediate between the bone acidic
proteins and dentin phosphophoryns. AG1 has numerous acidic consensus sites for phosphorylation by both casein kinases I and
II. Immunochemical and organ culture biosynthetic studies show that AG1 is present in phosphorylated form at low levels in
the dentin matrix. If fully phosphorylated, AG1 would bear a net charge of -175/molecule of 473 residues. AG1 contains single
RGD integrin binding and N-glycosylation sequences. The overall picture that emerges is that of a matrix-associated acidic
phosphoprotein, with a potentially high calcium ion binding capacity, present at levels compatible with a regulatory role
in dentin mineralization.