Nucleotide and deduced amino acid sequences of three (beta-keratins of Nile crocodile scales are presented. Using 5'- and 3'-RACE analysis, two cDNA sequences of 1 kb (Cr-gptrp-1) and 1.5 kb (Cr-gptrp-2) were determined, corresponding to 17.4 and 19.3 kDa proteins, respectively, and a pI of 8.0. In genomic DNA amplifications, we determined that the 5'-UTR of Cr-gptrp-2 contains an intron of 621 nucleotides. In addition, we isolated a third gene (Cr-gptrp-3) in genomic DNA amplifications that exhibits seven amino acid differences with Cr-gptrp-2. Genomic organization of the sequenced crocodilian beta-keratin genes is similar to avian beta-keratin genes. Deduced proteins are rich in glycine, proline, serine, and tyrosine, and contain cysteines toward the N- and C-terminal regions, likely for the formation of disulfide bonds. Prediction of the secondary structure suggests that the central core box of 20 amino acids contains two beta-strands and has 75-90% identity with chick beta-keratins. Toward the C-terminus, numerous glycine-glycine-tyrosine and glycine-glycine-leucine repeats are present, which may contribute to making crocodile scales hard. In situ hybridization shows expression of beta-keratin genes in differentiating beta-cells of epidermal transitional layers. Phylogenetic analysis of the available archosaurian and lepidosaurian beta-keratins suggests that feather keratins diversified early from nonfeather keratins, deep in archosaur evolution. However, only the complete knowledge of all crocodilian beta-keratins will confirm whether feather keratins have an origin independent of those in bird scales, which preceded the split between birds and crocodiles. J Exp Zool (Mol. Dev. Evol.) 312B:42-57, 2009. (C) 2008 Wiley-Liss, Inc.

beta-Keratins of the Crocodilian Epidermis: Composition, Structure, and Phylogenetic Relationships / L., Dalla Valle; A., Nardi; C., Gelmi; Toni, Mattia; D., Emera; L., Alibardi. - In: JOURNAL OF EXPERIMENTAL ZOOLOGY. PART B, MOLECULAR AND DEVELOPMENTAL EVOLUTION.. - ISSN 1552-5007. - 312B:1(2009), pp. 42-57. [10.1002/jez.b.21241]

beta-Keratins of the Crocodilian Epidermis: Composition, Structure, and Phylogenetic Relationships

TONI, MATTIA;
2009

Abstract

Nucleotide and deduced amino acid sequences of three (beta-keratins of Nile crocodile scales are presented. Using 5'- and 3'-RACE analysis, two cDNA sequences of 1 kb (Cr-gptrp-1) and 1.5 kb (Cr-gptrp-2) were determined, corresponding to 17.4 and 19.3 kDa proteins, respectively, and a pI of 8.0. In genomic DNA amplifications, we determined that the 5'-UTR of Cr-gptrp-2 contains an intron of 621 nucleotides. In addition, we isolated a third gene (Cr-gptrp-3) in genomic DNA amplifications that exhibits seven amino acid differences with Cr-gptrp-2. Genomic organization of the sequenced crocodilian beta-keratin genes is similar to avian beta-keratin genes. Deduced proteins are rich in glycine, proline, serine, and tyrosine, and contain cysteines toward the N- and C-terminal regions, likely for the formation of disulfide bonds. Prediction of the secondary structure suggests that the central core box of 20 amino acids contains two beta-strands and has 75-90% identity with chick beta-keratins. Toward the C-terminus, numerous glycine-glycine-tyrosine and glycine-glycine-leucine repeats are present, which may contribute to making crocodile scales hard. In situ hybridization shows expression of beta-keratin genes in differentiating beta-cells of epidermal transitional layers. Phylogenetic analysis of the available archosaurian and lepidosaurian beta-keratins suggests that feather keratins diversified early from nonfeather keratins, deep in archosaur evolution. However, only the complete knowledge of all crocodilian beta-keratins will confirm whether feather keratins have an origin independent of those in bird scales, which preceded the split between birds and crocodiles. J Exp Zool (Mol. Dev. Evol.) 312B:42-57, 2009. (C) 2008 Wiley-Liss, Inc.
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beta-Keratins of the Crocodilian Epidermis: Composition, Structure, and Phylogenetic Relationships / L., Dalla Valle; A., Nardi; C., Gelmi; Toni, Mattia; D., Emera; L., Alibardi. - In: JOURNAL OF EXPERIMENTAL ZOOLOGY. PART B, MOLECULAR AND DEVELOPMENTAL EVOLUTION.. - ISSN 1552-5007. - 312B:1(2009), pp. 42-57. [10.1002/jez.b.21241]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/139154
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