Evolution of keratin genes: different protein domains evolve by different pathways

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Cell Biology

Background:

• Intermediate filaments (IFs) are a diverse class of cytoskeletal proteins originating from a common ancestral gene.
• IF proteins possess a conserved central alpha-helical domain flanked by variable N- and C-terminal domains.
• Subfamilies within the IF family are identifiable through immunological and nucleic acid hybridization methods.

Purpose of the Study:

• To present the genomic DNA sequence encoding a 65-kilodalton human keratin.
• To compare this keratin sequence with other intermediate-filament proteins.
• To elucidate the evolutionary mechanisms driving the diversification of intermediate-filament proteins.

Main Methods:

• Genomic DNA sequencing of a 65-kilodalton human keratin.
• Sequence homology analysis of intermediate-filament proteins.
• Comparative sequence analysis focusing on conserved and variable domains.

Main Results:

• The central, alpha-helical domains of intermediate-filament proteins exhibit significant homology, supporting a shared ancestry.
• The variable terminal domains display sequence divergence, indicating distinct evolutionary pathways.
• Specific mechanisms like tandem gene duplications and potential gene conversion events are implicated in the evolution of variable domains.

Conclusions:

• The conserved central domain reflects the ancient origin of intermediate filaments.
• The variable terminal domains have undergone independent evolutionary diversification.
• Understanding these evolutionary mechanisms provides insight into the functional specialization of intermediate-filament proteins.