Immunoelectron microscopic localization of the core protein of decorin near the d and e bands of tendon collagen fibrils by use of monoclonal antibodies.

Two monoclonal antibodies, 6D6 and 7B1, previously shown to recognize different epitopes on different regions of the protein core of decorin were used to localize the protein core in relation to the positively stained bands in the D period of bovine tendon collagen fibrils. Peroxidase-antiperoxidase staining revealed that the antigen is associated with the surface of all fibrils and suggested that the axial distance between antigens is D-periodic. Immunoferritin labeling with each antibody produced a distribution of ferritin particles that showed that both epitopes of the protein core are localized near the d and e bands in the D period. The data indicate that the decorin protein core binding site(s) on tendon collagen fibrils is/are located near these bands, axially, within the D period.