Isolation of a new class of cysteine-glycine-proline-rich beta-proteins (beta-keratins) and their expression in snake epidermis.
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.
Dalla Valle
Luisa
L
Dipartimento di Biologia, University of Padova, Padova, Italy.
Nardi
Alessia
A
Alibardi
Lorenzo
L
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
D053800:beta-Keratins; D011392:Proline; D003545:Cysteine; D005998:Glycine