Basement membrane collagen from bovine lung: its chain associations as observed by two-dimensional electrophoresis

A basement membrane collagen has been isolated from limited pepsin digests of bovine lung alveolar tissue by differential salt fractionation and DEAE-cellulose chromatography. Fractionation and characterization of the peptide chain fragments of the collagen have revealed the presence of two classes of collagen chains: one is 160K-1, 100K-1, and 80K-1 and the other is 100K-2 and 80K-2. Apparent isoelectric points of these chain fragments were 8.4, 8.6, 8.35-8.45, 8.9-9.0 and 8.9-9.0, respectively. Electrophoretic analysis on temperature dependent reductions of the collagen and its denaturation products has revealed the presence of disulfide bonds between collagen chain fragments of 160K-1-80K-2 and possibly 160K-1-160K-1 which require elevated temperatures for reduction and the bonds within 100K-2 fragments (80K-2-small fragments such as 10K-20K) and possibly between 80K-2-80K-2 which are reducible without elevated temperatures.