Modular origins of biological electron transfer chains

Area of Science:

• Biochemistry
• Structural Biology
• Evolutionary Biology

Background:

• Oxidoreductases are vital enzymes catalyzing essential electron transfer reactions for life.
• The evolutionary origins and ancestral building blocks of oxidoreductases remain largely unknown.
• Understanding these origins is key to deciphering the evolution of metabolic energy production.

Purpose of the Study:

• To identify the fundamental protein-metal modules that constitute modern oxidoreductases.
• To trace the evolutionary pathways of these modules from ancestral forms.
• To elucidate the origins of electron transfer chains in biological systems.

Main Methods:

• Comparative structural analysis of oxidoreductases.
• Clustering of cofactor microenvironments using transition metal-containing cofactors.
• Analysis of spatial adjacency networks (SPAN) in multi-cofactor oxidoreductases.

Main Results:

• Identified four major ancestral modules: bacterial ferredoxin, cytochrome c, symerythrin, and plastocyanin-type folds.
• Structural alignments suggest both homology and analogy in module evolution.
• SPAN analysis reveals modular units likely duplicated and diversified over evolutionary time.

Conclusions:

• A limited set of fundamental modules underpin the diversity of extant oxidoreductases.
• These modules likely originated in the Archean eon and evolved through duplication and diversification.
• The study provides insights into the early evolution of biological energy transfer mechanisms.