Snake scales contain specialized hard keratins (beta-keratins) and alpha- or cyto-keratins in their epidermis. The number, isoelectric point, and the evolution of these proteins in snakes and their similarity with those of other vertebrates are not known. In the present study, alpha- and beta-keratins of snake molts and of the whole epidermis have been studied by using two-dimensional electrophoresis and immunocytochemistry. Specific keratins in snake epidermis have been identified by using antibodies that recognize acidic and basic cytokeratins and avian or lizard scale beta-keratin. Alpha keratins of 40-70 kDa and isoelectric point (pl) at 4.5-7.0 are present in molts. The study suggests that cytokeratins in snakes are acidic or neutral, in contrast to mammals and birds where basic keratins are also present. Beta keratins of 10-15 kDa and a pI of 6.5-8.5 are found in molts. Some beta-keratins appear as basic proteins (pI 8.2) comparable to those present in the epidermis of other reptiles. Some basic "beta-keratins" associate with cytokeratins as matrix proteins and replace cytokeratins forming the corneous material of the mature beta-layer of snake scales, as in other reptiles. The study also suggests that more forms of beta-keratins (more than three different types) are present in the epidermis of snakes. (c) 2006 Elsevier GmbH. All rights reserved.