title: Modulation of coupling in the Escherichia coli ATP synthase by ADP and Pi: Role of the ε subunit C-terminal domain.
abstract: The ε-subunit of ATP-synthase is an endogenous inhibitor of the hydrolysis activity of the complex and its α-helical C-terminal domain (εCTD) undergoes drastic changes among at least two different conformations. Even though this domain is not essential for ATP synthesis activity, there is evidence for its involvement in the coupling mechanism of the pump. Recently, it was proposed that coupling of the ATP synthase can vary as a function of ADP and Piconcentration. In the present work, we have explored the possible role of the εCTD in this ADP- and Pi-dependent coupling, by examining an εCTD-lacking mutant of Escherichia coli. We show that the loss of Pi-dependent coupling can be observed also in the εCTD-less mutant, but the effects of Pion both proton pumping and ATP hydrolysis were much weaker in the mutant than in the wild-type. We also show that the εCTD strongly influences the binding of ADP to a very tight binding site (half-maximal effect≈1nM); binding at this site induces higher coupling in EFOF1and increases responses to Pi. It is proposed that one physiological role of the εCTD is to regulate the kinetics and affinity of ADP/Pibinding, promoting ADP/Pi-dependent coupling.
authors.affiliation: Department of Biology, Laboratory of Biochemistry and Biophysics, University of Bologna, Via Irnerio 42, 40126 Bologna, Italy.
authors.forename: M
authors.initials: M
authors.lastname: D'Alessandro
authors.affiliation: Department of Biology, Laboratory of Biochemistry and Biophysics, University of Bologna, Via Irnerio 42, 40126 Bologna, Italy. Electronic address: paola.turina@unibo.it.
authors.forename: P
authors.initials: P
authors.lastname: Turina
authors.affiliation: Department of Biology, Laboratory of Biochemistry and Biophysics, University of Bologna, Via Irnerio 42, 40126 Bologna, Italy.
authors.forename: B A
authors.initials: BA
authors.lastname: Melandri
authors.affiliation: Department of Biochemistry, University of Western Ontario, London, Ontario N6A 5C1, Canada.
authors.forename: S D
authors.initials: SD
authors.lastname: Dunn
mesh_terms: D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D001665:Binding Sites / Q000502:physiology; D004926:Escherichia coli / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D000072417:Protein Domains / Q000502:physiology; D017494:Proton Pumps / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D011522:Protons
chemical_list: D017494:Proton Pumps; D011522:Protons; C035135:periodate-oxidized ADP; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases
keywords: ADP binding; ATP synthase; Activation; E. coli; Uncoupling; ε subunit