electron-microscopical autoradiography and cytochemical techniques have been used to identify the distinct and separate subcellular structures involved in the secretion of 1 ) procollagen , 2 ) dihydroxyphenylalanine ( dopa ) , which is a precursor of a collagen-crosslinking compound , and 3 ) dopa oxidase , which converts dopa to a putative crosslinking compound of collagen in the axial skeleton of the gorgonian coral leptogorgia virulata .
C0033235
procollagen
C0009325
collagen