Proteodermatan and proteokeratan sulfate (decorin, lumican/fibromodulin) proteins are horseshoe shaped. Implications for their interactions with collagen.

The small proteoglycans proteodermatan and proteokeratan sulfates organize collagen fibrils in extracellular matrix [Scott, J. E. (1992) FASEB J. 6, 2639-2645], thus helping to maintain tissue shape. Their interaction with fibrils is probably via the protein. They have been examined by rotary shadowing-electron microscopy, which showed that these leucine-rich-repeat proteins are horseshoe shaped. Morphometry and comparison with polypeptide sequences suggest ways in which decorin could interact with tissue collagen fibrils. It is proposed that decorin is a bidentate ligand attached to two parallel neighboring collagen molecules in the fibril, helping to stabilize fibrils and orient fibrillogenesis.