Isolation and partial characterization of bovine gingival AB collagen

Limited proteolysis with pepsin solubilized 25% of the insoluble gingival matrix as mainly soluble collagenous material. Fractional salt precipitation at neutral pH resulted in the separation of types III and I at 1.8 and 2.6 M NaCl, respectively. In addition, a collagenous fraction accounting for 2% of the solubilized collagen and precipitating at 4.5 M NaCl was shown to be identical with type V collagen. Isolation and partial characterization of the constituent-alpha-chains of the 4.5 M PPT by gel filtration, ion exchange and hydroxylapatite chromatography as well as disc electrophoresis showed that gingival type V collagen contains alpha A and alpha B chains in a ratio alpha B/alpha A of 1.73-1.8. Electron microscopic examination of ATP-precipitates showed that this collagen type gave only one kind of SLS aggregates with asymmetric band pattern characteristically different from that of type I collagen. The data provide evidence that gingival AB collagen is a heteropolymer in which the alpha A and alpha B chains are assembled in the same macromolecule in a 1:2 ratio.