β‐keratins of differentiating epidermis of snake comprise glycine‐proline‐serine‐rich proteins with an avian‐like gene organization

β‐keratins of reptilian scales have been recently cloned and characterized in some lizards. Here we report for the first time the sequence of some β‐keratins from the snake Elaphe guttata . Five different cDNAs were obtained using 5′‐ and 3′‐RACE analyses. Four sequences differ by only few nucleotides in the coding region, whereas the last cDNA shows, in this region, only 84% of identity. The gene corresponding to one of the cDNA sequences has a single intron present in the 5′‐untranslated region. This genomic organization is similar to that of birds' β‐keratins. Cloning and Southern blotting analysis suggest that snake β‐keratins belong to a family of high‐related genes as for geckos. PCR analysis suggests a head‐to‐tail orientation of genes in the same chromosome. In situ hybridization detected β‐keratin transcripts almost exclusively in differentiating oberhautchen and β‐cells of the snake epidermis in renewal phase. This is confirmed by Northern blotting that showed, in this phase, a high expression of two different transcripts whereas only the longer transcript is expressed at a much lower level in resting skin. The cDNA coding sequences encoded putative glycine‐proline‐serine rich proteins containing 137–139 amino acids, with apparent isoelectric point at 7.5 and 8.2. A central region, rich in proline, shows over 50% homology with avian scale, claw, and feather keratins. The prediction of secondary structure shows mainly a random coil conformation and few β‐strand regions in the central region, likely involved in the formation of a fibrous framework of β‐keratins. This region was possibly present in basic reptiles that originated reptiles and birds. Developmental Dynamics 236:1939–1953, 2007. © 2007 Wiley‐Liss, Inc.