Detection of subunit interfacial modifications by tracing the evolution of clamp-loader complex

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Biochemistry

Background:

• Clamp-loader and clamp proteins are essential for DNA replication in archaea and eukaryotes.
• Understanding the evolutionary relationship between archaeal and eukaryotic protein complexes can illuminate conserved biological mechanisms.

Purpose of the Study:

• To investigate the evolutionary history of archaeal and eukaryal clamp-loader and clamp proteins.
• To determine the phylogenetic relationship between archaeal and eukaryotic clamp-loader complexes.
• To identify conserved evolutionary modifications at the protein subunit interfaces.

Main Methods:

• Application of the evolutionary trace method to analyze protein sequences.
• Construction of molecular phylogenies for clamp-loader and clamp proteins.
• Analysis of amino acid replacement patterns at subunit interfaces.

Main Results:

• The archaeal hetero-pentameric clamp-loader (with two subunits) is likely a degenerated form of the five-subunit eukaryotic complex (RFC1-5).
• Amino acid replacements accumulated preferentially at the interfaces between protein subunits during evolution.
• Specific interfacial modifications crucial for subunit interaction are conserved in extant complexes.

Conclusions:

• The evolutionary trajectory of clamp-loader complexes suggests a reduction in subunit complexity in the archaeal lineage.
• Subunit interface regions are critical evolutionary hotspots for protein complex evolution and functional adaptation.
• Conserved interfacial modifications highlight their importance in maintaining the functional integrity of the clamp-loader complex.