7S domain constitutes the amino-terminal end of type IV collagen: an immunochemical study

The collagenous material from bovine kidney cortex was prepared by pepsin digestion of cortex homogenates. The 7S collagen was isolated after bacterial collagenase digestion of collagenous basement membrane material and was further purified by molecular sieve and ion exchange chromatography. The antibodies were raised in rabbits against a purified 7S collagen preparation. The pepsin-derived collagenous fragments alpha 1(IV)130K, 95K and alpha 2(IV)120K prepared from bovine cortex were tested for their cross-reactivity with the antiserum. The fragment alpha 1(IV)130K was found to be significantly cross-reactive. The results show the presence of common structural antigenic determinants between 7S collagen and alpha 1(IV)130K fragment, thus indicating that 7S collagen is located at the amino-terminal end of type IV collagen.