Functional asymmetry of the F-0 motor in bacterial ATP synthases
2009 (English)In: Molecular Microbiology, ISSN 0950-382X, E-ISSN 1365-2958, Vol. 72, no 2, 479-490 p.Article in journal (Refereed) Published
F1F0 ATP synthases use the electrochemical potential of H+ or Na+ across biological membranes to synthesize ATP by a rotary mechanism. In bacteria, the enzymes can act in reverse as ATP-driven ion pumps creating the indispensable membrane potential. Here, we demonstrate that the F-0 parts of a Na+- and H+-dependent enzyme display major asymmetries with respect to their mode of operation, reflected by the requirement of similar to 100 times higher Na+ or H+ concentrations for the synthesis compared with the hydrolysis of ATP. A similar asymmetry is observed during ion transport through isolated F-0 parts, indicating different affinities for the binding sites in the a/c interface. Together with further data, we propose a model that provides a rationale for a differential usage of membrane potential and ion gradient during ATP synthesis as observed experimentally. The functional asymmetry might also reflect an important property of the ATP synthesis mechanism in vivo. In Escherichia coli, we observed respiratory chain-driven ATP production at pH 7-8, while P-site pH values < 6.5 were required for ATP synthesis in vitro. This discrepancy is discussed with respect to the hypothesis that during respiration lateral proton diffusion could lead to significant acidification at the membrane surface.
Place, publisher, year, edition, pages
2009. Vol. 72, no 2, 479-490 p.
electrochemical proton gradient, escherichia-coli, propionigenium-modestum, adenosine-triphosphatase, energy transduction, h+-atpase, delta-ph, membrane, subunit, interface
IdentifiersURN: urn:nbn:se:su:diva-60232DOI: 10.1111/j.1365-2958.2009.06658.xISI: 000265014500018OAI: oai:DiVA.org:su-60232DiVA: diva2:434497
authorCount :32011-08-152011-08-112011-08-15Bibliographically approved