A chondroitin sulfate chain attached to the bone dentin matrix protein 1 NH2-terminal fragment.
Dentin matrix protein 1 (DMP1) is an acidic noncollagenous protein shown by gene ablations to be critical for the proper mineralization of bone and dentin. In the extracellular matrix of these tissues DMP1 is present as fragments representing the NH2-terminal (37 kDa) and COOH-terminal (57 kDa) portions of the cDNA-deduced amino acid sequence. During our separation of bone noncollagenous proteins, we observed a high molecular weight, DMP1-related component (designated DMP1-PG). We purified DMP1-PG with a monoclonal anti-DMP1 antibody affinity column. Amino acid analysis and Edman degradation of tryptic peptides proved that the core protein for DMP1-PG is the 37-kDa fragment of DMP1. Chondroitinase treatments demonstrated that the slower migration rate of DMP1-PG is due to the presence of glycosaminoglycan. Quantitative disaccharide analysis indicated that the glycosaminoglycan is made predominantly of chondroitin 4-sulfate. Further analysis on tryptic peptides led us to conclude that a single glycosaminoglycan chain is linked to the core protein via Ser74, located in the Ser74-Gly75 dipeptide, an amino acid sequence specific for the attachment of glycosaminoglycans. Our findings show that in addition to its existence as a phosphoprotein, the NH2-terminal fragment from DMP1 occurs as a proteoglycan. Amino acid sequence alignment analysis showed that the Ser74-Gly75 dipeptide and its flanking regions are highly conserved among a wide range of species from caiman to the Homo sapiens, indicating that this glycosaminoglycan attachment domain has survived an extremely long period of evolution pressure, suggesting that the glycosaminoglycan may be critical for the basic biological functions of DMP1.
Qin
Chunlin
C
Department of Endodontics, University of Texas Houston Health Science Center Dental Branch, Houston, Texas 77030, USA. Chunlin.Qin@uth.tmc.edu
Huang
Bingzhen
B
Wygant
James N
JN
McIntyre
Bradley W
BW
McDonald
Charles H
CH
Cook
Richard G
RG
Butler
William T
WT
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D015153:Blotting, Western; D001842:Bone and Bones / Q000378:metabolism; D002809:Chondroitin Sulfates / Q000737:chemistry*; D002810:Chondroitinases and Chondroitin Lyases / Q000737:chemistry; D002845:Chromatography; D018076:DNA, Complementary / Q000378:metabolism; D004187:Disaccharides / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D016326:Extracellular Matrix Proteins / Q000737:chemistry*; D005998:Glycine / Q000737:chemistry; D006025:Glycosaminoglycans / Q000737:chemistry; D006801:Humans; D008969:Molecular Sequence Data; D019158:N-Acetylneuraminic Acid / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D051381:Rats; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry; D013431:Sulfates / Q000737:chemistry; D014357:Trypsin / Q000737:chemistry / Q000494:pharmacology
D000596:Amino Acids; C513309:DMP1 protein, human; D018076:DNA, Complementary; D004187:Disaccharides; C081635:Dmp1 protein, rat; D016326:Extracellular Matrix Proteins; D006025:Glycosaminoglycans; D010710:Phosphates; D010750:Phosphoproteins; D013431:Sulfates; D012694:Serine; D002809:Chondroitin Sulfates; D014357:Trypsin; D002810:Chondroitinases and Chondroitin Lyases; C446037:chondroitinase B; D019158:N-Acetylneuraminic Acid; D005998:Glycine