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Evolution of the F0F1 ATP Synthase Complex in Light of the Patchy Distribution of Different Bioenergetic Pathways across Prokaryotes
Vassiliki Lila Koumandou, Sophia Kossida
2014 DOI: 10.1371/journal.pcbi.1003821
Bacteria and archaea are characterized by an amazing metabolic diversity, which allows them to persist in diverse and often extreme habitats. Apart from oxygenic photosynthesis and oxidative phosphorylation, well-studied processes from chloroplasts and mitochondria of plants and animals, prokaryotes utilize various chemo- or lithotrophic modes, such as anoxygenic photosynthesis, iron oxidation and reduction, sulfate reduction, and methanogenesis. Most bioenergetic pathways have a similar general structure, with an electron transport chain composed of protein complexes acting as electron donors and acceptors, as well as a central cytochrome complex, mobile electron carriers, and an ATP synthase. While each pathway has been studied in considerable detail in isolation, not much is known about their relative evolutionary relationships.
Our results indicate an ancient origin of this protein complex, and no clustering based on bioenergetic mode, which suggests that no special modifications are needed for the ATP synthase to work with different electron transport chains. Moreover, examination of the ATP synthase genetic locus indicates various gene rearrangements in the different bacterial lineages, ancient duplications of atpI and of the beta subunit of the F0 subcomplex, as well as more recent stochastic lineage-specific and species-specific duplications of all subunits.
if different bioenergetic pathways dispersed into different lineages by horizontal gene transfer, this did not involve the ATP synthase complex. Presumably, each species used its pre-existing ATP synthase complex and adapted it to utilize the proton gradient generated by vastly different ETCs.
A more thorough structural analysis would be needed to examine if certain structural modifications unite the ATP synthases of organisms using each bioenergetic pathway.
Given the ancient origin of the F0F1 ATPase, the phylogenetic trees can perhaps give clues as to the evolutionary relationships between different bacterial lineages. The branching order of bacterial lineages remains an issue unresolved through phylogenetic analysis
the ATP synthase cannot be used to reconstruct the origin of the diversity of bioenergetic modes in prokaryotes.
The F0F1 ATP synthase genetic locus is overall well conserved, although as demonstrated by multiple splits and duplications, in principle, the system is robust and flexible, as it can deal with a split between any subunits and/or a duplication of any subunit. The elucidation of the way in which certain species deal with these duplications, splits and losses, and the advantage any of these may confer, now requires further study.
Common Design 