Isolation and characterization of 15K noncollagenous protein from bovine periodontal ligament.

In pursuit of the nature of noncollagenous proteins (NCP) and their biosynthesis in periodontal ligament (PDL), isolation, characterization and a short incubation study were made on the PDL of the bovine mandibular incisors. A sodium chloride extract from the PDL contained several noncollagenous protein components. Eliminating serum derived proteins by a cross-reaction with antibody against bovine serum proteins, a protein estimated to be 15K on 5-15% gradient NaDodSO4-gel was the major constituent in the extract. This protein was isolated by sequential chromatography using Sepharose CL-6B and Sephacryl S-200 under dissociative conditions (4M guanidium hydrochloride). A chemical analysis of the protein showed that it was rich in aspartic acid, glutamic acid, glycine, alanine, leucine and lysine, and contained 5% sugars. Antibody directed against the purified PDL 15K protein reacted with the 15K protein, but no cross-reaction was observed with other components from the bovine PDL. A biosynthetic study of the protein using a short incubation with 3H-leucine indicated that the PDL cells produced the 15K protein and secreted it into the medium.