title: Isolation of a new class of cysteine-glycine-proline-rich beta-proteins (beta-keratins) and their expression in snake epidermis.
abstract: Scales of snakes contain hard proteins (beta-keratins), now referred to as keratin-associated beta-proteins. In the present study we report the isolation, sequencing, and expression of a new group of these proteins from snake epidermis, designated cysteine-glycine-proline-rich proteins. One deduced protein from expressed mRNAs contains 128 amino acids (12.5 kDa) with a theoretical pI at 7.95, containing 10.2% cysteine and 15.6% glycine. The sequences of two more snake cysteine-proline-rich proteins have been identified from genomic DNA. In situ hybridization shows that the messengers for these proteins are present in the suprabasal and early differentiating beta-cells of the renewing scale epidermis. The present study shows that snake scales, as previously seen in scales of lizards, contain cysteine-rich beta-proteins in addition to glycine-rich beta-proteins. These keratin-associated beta-proteins mix with intermediate filament keratins (alpha-keratins) to produce the resistant corneous layer of snake scales. The specific proportion of these two subfamilies of proteins in different scales can determine various degrees of hardness in scales.
authors.affiliation: Dipartimento di Biologia, University of Padova, Padova, Italy.
authors.forename: Luisa
authors.initials: L
authors.lastname: Dalla Valle
authors.forename: Alessia
authors.initials: A
authors.lastname: Nardi
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Alibardi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D049109:Cell Proliferation; D003001:Cloning, Molecular; D003545:Cysteine; D004817:Epidermis / Q000254:growth & development / Q000378:metabolism*; D015870:Gene Expression / Q000235:genetics; D005998:Glycine; D018978:Molting; D011392:Proline; D017422:Sequence Analysis, DNA; D012911:Snakes / Q000235:genetics* / Q000378:metabolism; D053800:beta-Keratins / Q000235:genetics* / Q000378:metabolism
chemical_list: D053800:beta-Keratins; D011392:Proline; D003545:Cysteine; D005998:Glycine