Acidic Structural Proteins of Connective Tissue

Abstract

From the insoluble structural matrix of skin and other connective tissues the collagen was removed by collagenase digestion. The remaining acidic structural proteins were then separated from elastin by solubilization with 8 M urea followed by treatment with mercaptoethanol in 8 M urea. Sodium dodecylsulfate‐polyacrylamide electrophoresis demonstrated up to 15 bands in some samples. The molecular weights were in the range of 15000 to 88000. Partial resolution of this mixture was achieved by molecular sieve chromatography. Treatment with NaBH 4 converted most of the components into polypeptide chains with a molecular weight of 15000. The observed heterogeneity may thus reflect to some extent polymerization of the same polypeptide chain. The presence of different protein species is, however, suggested, since in gel diffusion two to four antigens were discernible. Most of them were destroyed by reduction. An antigen stable towards reduction could be demonstrated by passive hemagglutination. This antigen was, at least in the rat skin, common to the proteins of the urea as well as the urea‐mercaptoethanol extract.