Protoplasma

, Volume 251, Issue 4, pp 827–837 | Cite as

Immunolocalization of alpha-keratins and associated beta-proteins in lizard epidermis shows that acidic keratins mix with basic keratin-associated beta-proteins

Original Article
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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.

Keywords

Lizard Epidermis Keratins Associated beta-proteins Immunogold labeling 
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Notes

Acknowledgments

The study was in part self-supported (Comparative Histolab) and also with a Grant from the Italian Ministry of Education and Scientific Research (Grant 2008 AXS E-002). The electrophoretic separation and Western blotting were carried on at the Proteome Service Facility in the Department of Biology, University of Bologna (Dr. F. Boschetti).

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Copyright information

© Springer-Verlag Wien 2013

Authors and Affiliations

  1. 1.Comparative Histolab and Dipartimento di Biologia, Geologia e Scienze AmbientaliUniversity of BolognaBolognaItaly

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