The origins and evolution of eukaryotic proteins

Area of Science:

• Evolutionary biology
• Molecular biology
• Biochemistry

Background:

• Common ancestry of eukaryotes, archaebacteria, and eubacteria is supported by conserved proteins.
• Some proteins, like ubiquitin, are found in eukaryotes and archaebacteria but not eubacteria.
• Cytoskeletal proteins, such as actin and tubulin, are largely unique to eukaryotes.

Purpose of the Study:

• Investigate the evolutionary origins of eukaryotic cytoskeletal proteins.
• Address the apparent lack of sequence homology between eukaryotic cytoskeletal proteins and their prokaryotic counterparts.
• Explore potential explanations for the evolutionary divergence of these key proteins.

Main Methods:

• Amino acid sequence comparisons of conserved proteins across urkingdoms.
• Crystallographic analysis of actin and its homology to ATP-binding domains.
• Examination of bacterial fts proteins for potential relationships to actin and tubulin.

Main Results:

• Actin shows crystallographic homology to an ATP-binding domain in proteins common to all urkingdoms.
• No direct sequence resemblance is found between eukaryotic actin/tubulin and their presumed prokaryotic antecedents.
• Two bacterial fts proteins are identified as potentially related to actin and tubulin.

Conclusions:

• The evolutionary history of cytoskeletal proteins may involve periods of dramatically accelerated change.
• Eukaryotic cytoskeletal proteins might have evolved earlier than indicated by their sequence divergence.
• Further research is needed to fully elucidate the evolutionary pathways of these fundamental proteins.