The Columbia Encyclopedia, Sixth Edition. 2001-07.
scleroprotein
large class of protein molecules that are ordinarily insoluble in water. The scleroproteins are employed principally for architectural purposes in the living cell and are localized in the structural tissues of bone, hair, skin, wool, silk, nails, hooves, and feathers. The major subclasses of scleroproteins include the collagens, elastins, and keratins.
