Analysis has been made of the minor collagens which are solubilized by limited pepsin digestion of chicken sterna and which remain in solution after precipitation of type I1 collagen at 0.9 M NaCl-0.5 M HOAc. The precipitate obtained by further dialysis to 1.2 M NaCl-0.5 M HOAc was shown to contain the l a , 2a, and 3a chains previously isolated

Recently, we have isolated a new collagenous molecule from chicken hyaline cartilage after limited pepsin digestion. This molecule, which contains interchain disulfide bonds, has been called the high molecular weight fraction or HMW [Reese, C. A., & Mayne, R. (1981) Biochemistry 20, 5443-5448]. We now present a detailed model for the structure of HMW, the model being derived from analyses both of components of HMW obtained after denaturation either with or without reduction and from electron microscopic observation of replicas of HMW obtained after rotary shadowing. We propose that HMW is a typical, triple-helical collagen molecule of length 134 nm, in which one of the chains has been cleaved at a distance of 96 nm from one end of the triple helix, while the other two chains remain uncleaved. The result of this cleavage is the appearance of a recognizable kink in molecules of HMW when visualized after rotary shadowing.

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