Interspecies conservation of outer arm dynein intermediate chain sequences defines two intermediate chain subclasses

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Outer arm dynein is a crucial motor protein complex involved in ciliary and flagellar motility.
• Intermediate chains (ICs) are essential components of the outer arm dynein structure, but their evolutionary relationships are not fully understood.

Purpose of the Study:

• To investigate the evolutionary relationships between sea urchin and Chlamydomonas outer arm dynein intermediate chains.
• To determine if structural differences among ICs are conserved in evolutionarily distant species.

Main Methods:

• Immunological analysis using antibodies against sea urchin outer arm dynein ICs.
• Isolation and sequencing of overlapping cDNAs encoding sea urchin IC2 and IC3.
• Sequence comparison between sea urchin and Chlamydomonas outer arm dynein ICs.

Main Results:

• Antibodies against sea urchin IC2 and IC3 cross-reacted with Chlamydomonas IC78 and IC69, respectively.
• Sequence analysis revealed significant homology between sea urchin IC2 and Chlamydomonas IC78 (45.8% identity), and sea urchin IC3 and Chlamydomonas IC69 (48.5% identity).
• Conservation of WD repeats in the C-terminal regions of all analyzed ICs, including cytoplasmic dynein IC74.

Conclusions:

• Structural differences among outer arm dynein intermediate chains are highly conserved across distantly related species.
• The findings establish a basis for the subclassification of dynein intermediate chains.
• This study provides the first evidence of conserved structural divergence in dynein ICs.