MODEL STRUCTURE OF DECORIN AND IMPLICATIONS FOR COLLAGEN FIBRILLOGENESIS

The three-dimensional structure of human decorin, a secreted proteogly can involved in the regulation of collagen fibrillogenesis and cellula r growth, has been modeled based on the crystal structure of the porci ne ribonuclease inhibitor. Both proteins contain leucine-rich repeats and share 18% identical residues. This model structure of decorin has an arch shape with the single glycosaminoglycan chain and the three N- linked oligosaccharides located on the same side of the molecule. Deco rin was modeled as binding to a polar sequence of collagen type I foun d in the d band. The inner concave surface is the appropriate size and shape to accommodate only one collagen triple helix of similar to 3 n m in length. The binding of one collagen triple helix to decorin is pr oposed to play a major role in the formation of the staggered arrangem ent of collagen molecules within the microfibrils by preventing latera l fusion of collagen molecules.