Type VI collagen beaded microfibrils from bovine cornea depolymerize at acidic pH, and depolymerization and polymerization are not influenced by hyaluronan.

Type VI collagen beaded microfibrils were extracted from bovine cornea or pig cartilage by limited collagenase digestion. Depolymerization of the microfibril, without strong denaturing reagents linke guanidinium hydrochloride or urea under mild acidic conditions, led to single tetramers and multiples of two to three. However, hyaluronidase digestion in accordance with a published method (Kielty et al. J. Cell Biol. 118:979-990, 1992) was unsuccessful in depolymerizing type VI collagen microfibrils. Also, repolymerization into microfibrils by incubation with hyaluronan was not observed. We further found no binding of native type VI collagen microfibrils to a hyaluronan-Sepharose column. Although a recombinant fragment comprising alpha 3(VI) domains N9-N2 showed apparent binding to the column, electron microscopy did not give any indication of binding of either type VI collagen or fragment N9-N2 to hyaluronan. The present findings suggest that the role of hyaluronan in polymerization of type VI collagen has been overestimated in previous work.