Biochemistry, Department of


Date of this Version



Published in Journal of the Royal Society Interface 11: 20140196 (2014); doi: 10.1098/ rsif.2014.0196


Copyright © 2014 Anne-Lise Ducluzeau, Barbara Schoepp-Cothenet, Robert van Lis, Frauke Baymann, Michael J. Russell, and Wolfgang Nitschke; published by the Royal Society. Used by permission.


Complex life on our planet crucially depends on strong redox disequilibria afforded by the almost ubiquitous presence of highly oxidizing molecular oxygen. However, the history of O2-levels in the atmosphere is complex and prior to the Great Oxidation Event some 2.3 billion years ago, the amount of O2 in the biosphere is considered to have been extremely low as compared with present-day values. Therefore the evolutionary histories of life and of O2-levels are likely intricately intertwined. The obvious biological proxy for inferring the impact of changing O2-levels on life is the evolutionary history of the enzyme allowing organisms to tap into the redox power of molecular oxygen, i.e. the bioenergetic O2 reductases, alias the cytochrome and quinol oxidases. Consequently, molecular phylogenies reconstructed for this enzyme superfamily have been exploited over the last two decades in attempts to elucidate the interlocking between O2 levels in the environment and the evolution of respiratory bioenergetic processes. Although based on strictly identical datasets, these phylogenetic approaches have led to diametrically opposite scenarios with respect to the history of both the enzyme superfamily and molecular oxygen on the Earth. In an effort to overcome the deadlock of molecular phylogeny, we here review presently available structural, functional, palaeogeochemical and thermodynamic information pertinent to the evolution of the superfamily (which notably also encompasses the subfamily of nitric oxide reductases). The scenario which, in our eyes, most closely fits the ensemble of these non-phylogenetic data, sees the low O2-affinity SoxM- (or A-) type enzymes as the most recent evolutionary innovation and the high-affinity O2 reductases (SoxB or B and cbb3 or C) as arising independently from NO-reducing precursor enzymes.

Ducluzeau rsif20140196supp1.aln (826 kB)
Multiple sequence alignment of NO- and O2-reductases

Ducluzeau rsif20140196supp2.pdb (3747 kB)
3D-alignment of 5 representatives from the superfamily's major clades

Ducluzeau (5 kB)
Phylogenetic tree in phb-format of the entire superfamily

Ducluzeau rsif20140196supp4.txt (58 kB)
Entry numbers and amino acid sequences of NOR-related sequences

Ducluzeau rsif20140196supp5.doc (23 kB)
Tree reconstruction methods