Hydroxyproline stabilizes the triple helix of chick tendon collagen

The thermal stability of unhydroxylated procollagen relative to hydroxylated procollagen was investigated using pepsin digestion at various temperatures in the interval 15° to 35° as an enzymatic probe of conformation. The results demonstrate that the unhydroxylated molecules thermally denature between 20° and 25°, while the hydroxylated molecules are stable at least to 35°. This finding suggests that the presence of hydroxyproline in the molecule contributes significantly to the thermal stability of collagen. The results also suggest that triple strand formation may be required for normal secretion.