Type IV collagen contains two distinct chains in separate molecules.

Type IV collagen from the EHS sarcoma, a basement membrane producing tumor, was characterized. Acid extracts of tumor grown in lathyritic animals contain proteins with two predominant collagen chains of apparent molecular weights of 160,000 and 140,000 daltons, designated alpha 1(IV) and alpha 2(IV). In addition, dimers and larger polymers formed by covalent crosslinking of the alpha 1(IV) and alpha 2 (IV) chains are also present. These two chains were found to be distinct from one another in amino acid composition and in the peptide patterns obtained following treatment with cyanogen bromide and S. aureus V8 protease. Precipitation of native collagen from acid solutions by the stepwise addition of NaCl yielded mixtures of the two chains with varying ratios suggesting that the two chains reside in different macromolecules.