Universal and Lineage-Specific Patterns in the Distribution of ECOD Domain Homology Groups Across Superkingdoms

Area of Science:

• Structural biology
• Evolutionary biology
• Bioinformatics

Background:

• Proteins are composed of modular domains, crucial for structure and evolution.
• The global distribution of these protein domains across life's lineages is not well understood.

Purpose of the Study:

• To map the distribution of protein domain homology groups (H-groups) across major life superkingdoms.
• To understand the evolutionary relationships and adaptive strategies reflected in protein domain architecture.

Main Methods:

• Utilized the Evolutionary Classification of Protein Domains (ECOD) database.
• Analyzed 1.16 million domains across 44 proteomes from Eukaryota, Bacteria, and Archaea.
• Categorized H-groups as universal, shared, or lineage-specific.

Main Results:

• Identified 3320 H-groups, with 126 (3.8%) forming a universal structural core across all three superkingdoms.
• Observed distinct fold architecture distributions: α/β in universal groups, α-rich in eukaryotes, and β-rich in bacteria.
• Revealed evolutionary connections, including bacterial systems in eukaryotes and archaeal machinery in eukaryotic nuclei.

Conclusions:

• Life's essential architecture relies on a conserved set of ancient protein folds.
• Lineage-specific diversity arises from recombination and functional diversification of existing domains.
• Protein domain analysis provides a quantitative, structure-based view of evolutionary history.