Forty keratin‐associated β‐proteins (β‐keratins) form the hard layers of scales, claws, and adhesive pads in the green anole lizard, Anolis carolinensis

Abstract

Using bioinformatic methods we have detected the genes of 40 keratin-associated beta-proteins (KAbetaPs) (beta-keratins) from the first available draft genome sequence of a reptile, the lizard Anolis carolinensis (Broad Institute, Boston). All genes are clustered in a single but not yet identified chromosomal locus, and contain a single intron of variable length. 5'-RACE and RT-PCR analyses using RNA from different epidermal regions show tissue-specific expression of different transcripts. These results were confirmed from the analysis of the A. carolinensis EST libraries (Broad Institute). Most deduced proteins are 12-16 kDa with a pI of 7.5-8.5. Two genes encoding putative proteins of 40 and 45 kDa are also present. Despite variability in amino acid sequences, four main subfamilies can be described. The largest subfamily includes proteins high in glycine, a small subfamily contains proteins high in cysteine, a third large subfamily contains proteins high in cysteine and glycine, and the fourth, smallest subfamily comprises proteins low in cysteine and glycine. An inner region of high amino acid identity is the most constant characteristic of these proteins and maps to a region with two to three close beta-folds in the proteins. This beta-fold region is responsible for the formation of filaments of the corneous material in all types of scales in this species. Phylogenetic analysis shows that A. carolinensis KAbetaPs are more similar to those of other lepidosaurians (snake, lizard, and gecko lizard) than to those of archosaurians (chick and crocodile) and turtles.

Identification and comparative analysis of the epidermal differentiation complex in snakes

“…It is syntenic with the CBP locus of the green anole lizard and with the main CBP loci of birds and turtles3033. Within the CBP gene cluster, 35 and 36 CBP genes, here termed Beta1 through Beta36 in order of the arrangement of the genes, were identified in the python and cobra, respectively, which is comparable to the 40 CBP genes present in the green anole lizard26, but lower than the 71 CBP genes reported for the Japanese gecko39.…”

“…The comparative analysis of snake EDCs suggests that the epidermis of snakes contains many more proteins than the small set of CBPs (beta-keratins) identified in previous studies2526. Both the number of CBPs and the number of other EDC genes of snakes is similar to those of the green anole lizard, and the total number and sequence diversification of epidermal differentiation genes (including CBPs) in snakes exceeds that present in mammals (Fig.…”

“…Both the python and cobra have an ortholog of the lizard gene Beta1 , previously termed Li-Ac40 26 (Fig. 2).…”

“…Corneous beta-proteins, traditionally called beta-keratins, have been identified as components of the epidermis in snakes, like in other reptiles22252627. Keratin intermediate filament proteins, previously referred to as alpha-keratins, are the main cytoskeletal proteins in the epidermis and skin appendages of vertebrates.…”

Redox Capacity of an Extracellular Matrix Protein Associated with Adhesion in Mytilus californianus

“…Although the analysis is incomplete, the β-sheet fold may be bifunctional, offering, on one hand, a blueprint for self-assembly already widely associated with the β-sheet-rich amyloid fibrils 34 and the cysteine and β-sheet-rich β-keratins 36 and, on the other, a structure conducive to electron shuttling as in α-crystallins. 37–39 …”