Characterization of a γ -Carboxyglutamic Acid-Containing Protein from Bone

A γ -carboxyglutamic acid-containing protein has been purified from the calcified tissues of several vertebrates. The presence of three γ -carboxyglutamic acid residues in the bovine protein was established by alkaline hydrolysis and amino acid analysis, a method based upon studies with synthetic γ...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1976-05, Vol.73 (5), p.1447-1451
Main Authors: Price, Paul A., Otsuka, Allen S., Poser, James W., Kristaponis, Joanne, Raman, Neerja
Format: Article
Language:English
Subjects:
Age Factors
Amino Acid Sequence
Amino acids
Animals
Bones
Calcification, Physiologic - drug effects
Calcium
Calcium phosphates
Cattle
Crystallization
Crystals
Dentin - analysis
Depression, Chemical
Female
Femur - analysis
Fishes
Gels
Humans
Hydrolysis
Hydroxyapatites - metabolism
Lipoproteins - biosynthesis
Male
Phosphates
Proteins - analysis
Proteins - isolation & purification
Proteins - metabolism
Proteins - pharmacology
Tricarboxylic Acids
Ungulates
Vitellogenins - biosynthesis
Vitellogenins - blood
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Summary:A γ -carboxyglutamic acid-containing protein has been purified from the calcified tissues of several vertebrates. The presence of three γ -carboxyglutamic acid residues in the bovine protein was established by alkaline hydrolysis and amino acid analysis, a method based upon studies with synthetic γ -carboxyglutamic acid. The identity of γ -carboxyglutamic acid in the bovine protein was established by mass spectroscopy on the unknown amino acid isolated from alkaline hydrolysates. The protein is extracted from finely ground bone during demineralization with EDTA, and purified from EDTA extracts by gel filtration over Sephadex G-100 and chromatography on DEAE-Sephadex. The protein has a 6800 molecular weight and an isoelectric point of pH 3.7. The amino-terminal 15 residues have been determined, and establish that this protein is not a fragment of the γ -carboxyglutamic acid-containing blood clotting factors. Similar γ -carboxyglutamic acid-containing proteins also have been purified from bovine dentine, swordfish vertebrae, and human tibia. No γ -carboxyglutamic acid can be detected in the calcified cartilage of elasmobranches, in calf epiphyseal growth cartilage, or in tooth enamel. The bovine protein binds strongly to hydroxyapatite but not to amorphous calcium phosphate, and it is a potent inhibitor of hydroxyapatite crystallization from supersaturated solutions of calcium and phosphate.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.73.5.1447