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  • Title: Immunolocalization of keratin-associated beta-proteins (beta-keratins) in scales of the reptiles Sphenodon punctatus indicates that different beta-proteins are present in beta- and alpha-layers.
    Author: Alibardi L.
    Journal: Tissue Cell; 2012 Dec; 44(6):378-84. PubMed ID: 22817772.
    Abstract:
    The present ultrastructural immunocytochemical study analyzes the localization of keratin-associated beta-proteins (beta-keratins) in the epidermis of the ancient reptile Sphenodon punctatus, a relict species adapted to mid-cold conditions. The epidermis comprises two main layers, indicated as beta- and alpha-keratin layers. The beta-layer contains small beta-proteins (beta-keratins) identified by using three different antibodies while the alpha-layer is poorly or not labeled for these proteins. Using other two antibodies directed against specific amino acid sequences identified in beta-proteins of lizard it results that a high-glycine beta-protein (HgG5) is specific for the beta-layer. Another antibody that recognizes glycine-cysteine medium-rich beta-proteins (HgGC10) immuno-stains beta- and alpha-layers. This pattern of distribution suggests that both beta- and alpha-layers contain beta-proteins of different types that associate and replace intermediate-filament alpha-keratins during the terminal differentiation of keratinocytes. Therefore the different epidermal layers of the epidermis in S. punctatus, characterized by a specific cytology, material properties and consistency appear to derive from the prevalent type of beta-proteins synthesized in each epidermal layer and not from the alternation between beta- and alpha-keratins. The present observations are discussed in comparison to previous results from lizard epidermis and indicate that beta-keratins correspond to keratin-associated proteins that through their internal beta-pleated region are capable to form filaments in addition to intermediate filaments keratins.
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