Isolation of a mRNA encoding a glycine‐proline–rich β‐keratin expressed in the regenerating epidermis of lizard

During scale regeneration in lizard tail, an active differentiation of β‐keratin synthesizing cells occurs. The cDNA and amino acid sequence of a lizard β‐keratin has been obtained from mRNA isolated from regenerating epidermis. Degenerate oligonucleotides, selected from the translated amino acid sequence of a lizard claw protein, were used to amplify a specific lizard keratin cDNA fragment from the mRNA after reverse transcription with poly dT primer and subsequent polymerase chain reaction (3′‐rapid amplification of cDNA ends analysis, 3′‐RACE). The new sequence was used to design specific primers to obtain the complete cDNA sequence by 5′‐RACE. The 835‐nucleotide cDNA sequence encodes a glycine‐proline–rich protein containing 163 amino acids with a molecular mass of 15.5 kDa; 4.3% of its amino acids is represented by cysteine, 4.9% by tyrosine, 8.0% by proline, and 29.4% by glycine. Tyrosine is linked to glycine, and proline is present mainly in the central region of the protein. Repeated glycine–glycine‐X and glycine‐X amino acid sequences are localized near the N‐amino and C‐terminal regions. The protein has the central amino acid region similar to that of claw–feather, whereas the head and tail regions are similar to glycine‐tyrosine–rich proteins of mammalian hairs. In situ hybridization analysis at light and electron microscope reveals that the corresponding mRNA is expressed in cells of the differentiating β‐layers of the regenerating scales. The synthesis of β‐keratin from its mRNA occurs among ribosomes or is associated with the surface of β‐keratin filaments. Developmental Dynamics 234:934–947, 2005. © 2005 Wiley‐Liss, Inc.