Evolutionary primacy of sodium bioenergetics

Area of Science:

• Biochemistry
• Molecular Biology
• Evolutionary Biology

Background:

• F- and V-type ATPases are rotary molecular machines crucial for ATP synthesis/hydrolysis.
• These ATPases can translocate either protons or sodium ions across membranes.
• Proton-dependent ATPases are common, while sodium-dependent ones are often seen as specialized adaptations.

Purpose of the Study:

• To investigate the evolutionary relationship between proton- and sodium-translocating ATPases.
• To clarify the ancestral mechanism of membrane bioenergetics.

Main Methods:

• Combined structural and phylogenetic analyses.
• Compared structures of membrane-embedded proteolipid rings in sodium-dependent F- and V-ATPases.
• Analyzed the distribution of sodium-dependent ATPases within phylogenetic trees.

Main Results:

• Identified nearly identical amino acid sets involved in sodium binding in both F- and V-type sodium-dependent ATPases.
• Found sodium-dependent ATPases interspersed among proton-dependent ones in phylogenetic trees for both F- and V-branches.

Conclusions:

• The use of sodium gradients for ATP synthesis appears to be the ancestral form of membrane bioenergetics.
• Primitive cell membranes likely utilized sodium transport before evolving proton impermeability and proton-tightness.
• The shift to using protons as the coupling ion seems to be a later evolutionary innovation that occurred multiple times independently.