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Type VI collagen beaded microfibrils from bovine cornea depolymerize at acidic pH, and depolymerization and
1Biocenter, University of Basel, Switzerland.
Abstract:
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.
Insights
Type VI collagen microfibrils depolymerize into tetramers under mild acidic conditions. Hyaluronan does not appear to play a significant role in type VI collagen polymerization, contrary to previous research.
Area of Science:
- Biochemistry
- Cell Biology
- Extracellular Matrix Research
Background:
- Type VI collagen forms beaded microfibrils crucial for tissue structure.
- Previous studies suggested a role for hyaluronan in type VI collagen polymerization.
Purpose of the Study:
- To investigate the role of hyaluronan in the polymerization of type VI collagen microfibrils.
- To determine the conditions for depolymerization and repolymerization of type VI collagen.
Main Methods:
- Limited collagenase digestion to extract type VI collagen microfibrils.
- Mild acidic conditions for microfibril depolymerization.
- Hyaluronidase digestion and hyaluronan-Sepharose chromatography to assess interactions.
Main Results:
- Type VI collagen microfibrils depolymerized into tetramers under mild acidic conditions.
- Hyaluronidase digestion did not depolymerize microfibrils.
- No binding of type VI collagen or its fragments to hyaluronan was observed.
Conclusions:
- The role of hyaluronan in type VI collagen polymerization may have been overestimated.
- Mild acidic conditions are sufficient for type VI collagen microfibril depolymerization.