Novel urinary fragments from human basement membrane collagen

Five fragments of collagen have been purified from human urine. The fragments cross-reacted with basement membrane collagen from pig kidney cortices when tested against antiserum to basement membrane collagen, type IV, from murine tumor. The concentrations of these fragments were sufficient for amino acid analysis, immunological analysis, and in one case, preliminary analytical amino acid sequencing. Compositional analysis of the fragments indicated concentrations of hydroxylysine, hydroxyproline, and glycine that are typical of collagen. High values of hexosamines and neutral sugars were also found. An NH ₂-terminal sequence of 18 residues was obtained for one fragment of M(r)~6,500. This sequence was unique among proteins reported to date, but was obviously collagen-like. A urinary source of basement membrane collagen fragments will permit molecular characterization of basement membrane in inherited or acquired diseases affecting this structure.