The hydroxyproline of elastin

Abstract The question of whether the hydroxyproline found in elastin represents contamination with collagen was studied by subjecting solubilized elastin (α- plus β-elastin) to prolonged collagenase digestion. No loss of hydroxyproline was seen, and it is concluded that hydroxyproline is indeed a constituent of elastin in which it occurs in a collagenase-resistant sequence. The origin of this elastin hydroxyproline was studied by comparing the rate of incorporation of [ 14 C]proline and hydroxy-[ 14 C]proline into hydroxyproline of dermal and aortic collagen and aortic elastin. As has been repeatedly demonstrated for collagen, it was found that proline is a far better precursor of elastin hydroxyproline than is hydroxyproline itself. Both proteins incorporated a small amount of labeled hydroxyproline directly.