Abstract
ATP synthase is a complex universal enzyme responsible for ATP synthesis across all kingdoms of life. The F-type ATP synthase has been suggested to have evolved from two functionally independent, catalytic (F1) and membrane bound (Fo), ancestral modules. While the modular evolution of the synthase is supported by studies indicating independent assembly of the two subunits, the presence of intermediate assembly products suggests a more complex evolutionary process. We analyzed the phylogenetic profiles of the human mitochondrial proteins and bacterial transcription units to gain additional insight into the evolution of the F-type ATP synthase complex. In this study, we report the presence of intermediary modules based on the phylogenetic profiles of the human mitochondrial proteins. The two main intermediary modules comprise the α3β3 hexamer in the F1 and the c-subunit ring in the Fo. A comprehensive analysis of bacterial transcription units of F1Fo ATP synthase revealed that while a long and constant order of F1Fo ATP synthase genes exists in a majority of bacterial genomes, highly conserved combinations of separate transcription units are present among certain bacterial classes and phyla. Based on our findings, we propose a model that includes the involvement of multiple modules in the evolution of F1Fo ATP synthase. The central and peripheral stalk subunits provide a link for the integration of the F1/Fo modules.
Highlights
Oxidative phosphorylation is the main source of ATP production in aerobic organisms
A large number of bacterial classes possess a long and highly conserved transcription unit, our results strongly suggest that the bacterial F1Fo ATP synthase genes evolved from several distinct transcription unit modules
ATPase complexes translated from the minor conserved transcription unit (cTU) were predicted as the actual F1Fo ATP synthase, because we simultaneously found no or partial A-type ATPase subunits in species with minor cTUs
Summary
Oxidative phosphorylation is the main source of ATP production in aerobic organisms. The redox reactions of the last step of aerobic respiration are performed by a series of evolutionary conserved protein complexes, or the electron transport chain (ETC). The main function of ETC is to produce a proton gradient across the cellular or mitochondrial membranes. ATP synthase utilizes this gradient to generate ATP (Mitchell 1961). Three types of ATP synthase have been identified: the A-, V-, and F-type ATPases. The A-type (A1Ao) ATPase exists in the archaea and a small number of bacteria (Ballmoos et al 2008; Lewalter and Muller 2006). The V-type (V1Vo) ATPase exists in the eukaryotic cytoplasmic membranes (vacuoles) (Beyenbach and Wieczorek 2006). The F-type (F1Fo) ATP synthase is found in
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