Dentin Phosphophoryn Binding to Collagen Fibrils

The interaction of rat incisor phosphophoryn with native turkey tendon collagen fibers has been examined by electron microscopy. The binding of phosphophoryn to the tendon fibril surfaces is quite selective. The phosphophoryn is seen as positively or negatively stained globular particles predominantly at the "e" band in the collagen gap region in transmission electron micrographs of the phosphophoryn-reacted fibrils. The selectivity of binding to the fibrils was obtained in the presence of calcium ions, which bind avidly to phosphophoryn. The specific association of phosphophoryn at the "e" band suggests a possible regulation of mineral deposition within the gap regions of the collagen fibrils.