A comparison of genomic coding sequences for feather and scale keratins: structural and evolutionary implications.

Area of Science:

• Developmental Biology
• Molecular Genetics
• Structural Biology

Background:

• Keratins are structural proteins crucial for epidermal development in vertebrates.
• Feathers and scales in birds are complex epidermal appendages with distinct keratin compositions.
• Understanding keratin gene evolution provides insights into appendage formation.

Purpose of the Study:

• To analyze DNA sequences of embryonic chick feather and scale keratin genes.
• To compare the deduced amino acid sequences and structural properties of feather and scale keratins.
• To investigate the evolutionary relationship between feather and scale keratin genes.

Main Methods:

• DNA sequencing of embryonic chick feather and scale keratin genes.
• Bioinformatic analysis of protein-coding regions and deduced amino acid sequences.
• Comparative analysis of sequence homology and structural features.

Main Results:

• High homology was found between feather and scale keratin gene protein-coding regions.
• Scale keratins are larger than feather keratins due to four additional 13-amino acid repeats rich in glycine and tyrosine.
• These repeats in scale keratins are likely located externally to the core filament, influencing tissue-specific aggregation.

Conclusions:

• Feather and scale keratin genes share a common ancestry.
• Feather-like keratin genes likely evolved from scale keratin genes through a single deletion event.
• Sequence differences, particularly the glycine-tyrosine-rich repeats, explain tissue-specific filament aggregation.