title: Immunolocalization of alpha-keratins and associated beta-proteins in lizard epidermis shows that acidic keratins mix with basic keratin-associated beta-proteins.
abstract: The differentiation of the corneous layers of lizard epidermis has been analyzed by ultrastructural immunocytochemistry using specific antibodies against alpha-keratins and keratin associated beta-proteins (KAbetaPs, formerly indicated as beta-keratins). Both beta-cells and alpha-cells of the corneous layer derive from the same germinal layer. An acidic type I alpha-keratin is present in basal and suprabasal layers, early differentiating clear, oberhautchen, and beta-cells. Type I keratin apparently disappears in differentiated beta- and alpha-layers of the mature corneous layers. Conversely, a basic type II alpha-keratin rich in glycine is absent or very scarce in basal and suprabasal layers and this keratin likely does not pair with type I keratin to form intermediate filaments but is weakly detected in the pre-corneous and corneous alpha-layer. Single and double labeling experiments show that in differentiating beta-cells, basic KAbetaPs are added and replace type-I keratin to form the hard beta-layer. Epidermal alpha-keratins contain scarce cysteine (0.2-1.4 %) that instead represents 4-19 % of amino acids present in KAbetaPs. Possible chemical bonds formed between alpha-keratins and KAbetaPs may derive from electrostatic interactions in addition to cross-linking through disulphide bonds. Both the high content in glycine of keratins and KAbetaPs may also contribute to increase the hydrophobicy of the beta- and alpha-layers and the resistance of the corneous layer. The increase of gly-rich KAbetaPs amount and the bonds to the framework of alpha-keratins give rise to the inflexible beta-layer while the cys-rich KAbetaPs produce a pliable alpha-layer.
authors.affiliation: Comparative Histolab and Dipartimento di Biologia, Geologia e Scienze Ambientali, University of Bologna, Bologna, Italy, lorenzo.alibardi@unibo.it.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Alibardi
mesh_terms: D000818:Animals; D004817:Epidermis / Q000378:metabolism*; D007633:Keratins / Q000378:metabolism*; D053530:Keratins, Type I / Q000378:metabolism*; D008116:Lizards / Q000378:metabolism*; D053800:beta-Keratins / Q000378:metabolism*
chemical_list: D053530:Keratins, Type I; D053800:beta-Keratins; D007633:Keratins