Authors : Lorenzo Alibardi and Mattia Toni
Abstract: Beta-keratins determine most of mechanical resistance of reptilian scales. The amino acid sequence of these proteins is not known for most reptiles. An antibody directed against a known 20-amino acid sequence (core-box) of avian beta-keratins has been utilized to detect whether this epitope is also present in reptilian beta-keratins. The epidermis of most tested species (lepidosaurians, tuatara, chelonians andcrocodilians) shows immunoreactivity in the beta-layer. In immunoblots, specific immunolabeled bands are seen, mainly within 10-25 kDa (beta-keratin range). Bidimensional gel electrophoresis shows that most beta-keratins are basic proteins and contain the epitope for the presence of a core-box. The core-box is conserved among reptile and bird beta-keratins and seems linked to their structural properties in the formation of hard keratin packets. The only exception is represented by the soft shelled-turtle (Tryonix spiniferus). The latter species probably lacks the core-box in its beta-keratin and therefore cannot accumulate beta-keratin packets in the corneous layer explaining the softness of its shell. The molecular analysis on some known beta-keratin sequences suggests that the core-box epitope is centrally located in beta-keratins.
Lorenzo Alibardi and Mattia Toni , 2007. Beta-Keratins of Reptilian Scales Share a Central Amino Acid Sequence Termed Core-Box . Research Journal of Biological Sciences, 2: 329-339.