Characterization of keratins and associated proteins involved in the corneification of crocodilian epidermis.
Crocodilian keratinocytes accumulate keratin and form a corneous cell envelope of which the composition is poorly known. The present immunological study characterizes the molecular weight, isoelectric point (pI) and the protein pattern of alpha- and beta-keratins in the epidermis of crocodilians. Some acidic alpha-keratins of 47-68 kDa are present. Cross-reactive bands for loricrin (70, 66, 55 kDa), sciellin (66, 55-57 kDa), and filaggrin-AE2-positive keratins (67, 55 kDa) are detected while caveolin is absent. These proteins may participate in the formation of the cornified cell membranes, especially in hinge regions among scales. Beta-keratins of 17-20 kDa and of prevalent basic pI (7.0-8.4) are also present. Acidic beta-keratins of 10-16 kDa are scarce and may represent altered forms of the original basic proteins. Crocodilian beta-keratins are not recognized by a lizard beta-keratin antibody (A68B), and by a turtle beta-keratin antibody (A685). This result indicates that these antibodies recognize specific epitopes in different reptiles. Conversely, crocodilian beta-keratins cross-react with the Beta-universal antibody indicating they share a specific 20 amino acid epitope with avian beta-keratins. Although crocodilian beta-keratins are larger proteins than those present in birds our results indicate presence of shared epitopes between avian and crocodilian beta-keratins which give good indication for the future determination of the sequence of these proteins.
Alibardi
L
L
Dipartimento di Biologia, Sezione Anatomia, Comparata, via Selmi 3, 40126, University of Bologna, 40126 Bologna, Italy. alibardi@biblio.cib.unibo.it
Toni
M
M
D000489:Alligators and Crocodiles / Q000033:anatomy & histology / Q000378:metabolism*; D000818:Animals; D000918:Antibody Specificity / Q000276:immunology; D001717:Birds / Q000378:metabolism; D003429:Cross Reactions / Q000276:immunology; D004817:Epidermis / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D000939:Epitopes / Q000276:immunology; D019143:Evolution, Molecular; D007526:Isoelectric Point; D015603:Keratinocytes / Q000378:metabolism* / Q000648:ultrastructure; D007633:Keratins / Q000737:chemistry* / Q000276:immunology / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008970:Molecular Weight; D053800:beta-Keratins / Q000737:chemistry / Q000276:immunology / Q000648:ultrastructure
D000939:Epitopes; D053800:beta-Keratins; D007633:Keratins