title: Single Enzyme Experiments Reveal a Long-Lifetime Proton Leak State in a Heme-Copper Oxidase.
abstract: Heme-copper oxidases (HCOs) are key enzymes in prokaryotes and eukaryotes for energy production during aerobic respiration. They catalyze the reduction of the terminal electron acceptor, oxygen, and utilize the Gibbs free energy to transport protons across a membrane to generate a proton (ΔpH) and electrochemical gradient termed proton motive force (PMF), which provides the driving force for the adenosine triphosphate (ATP) synthesis. Excessive PMF is known to limit the turnover of HCOs, but the molecular mechanism of this regulatory feedback remains relatively unexplored. Here we present a single-enzyme study that reveals that cytochrome bo3 from Escherichia coli, an HCO closely homologous to Complex IV in human mitochondria, can enter a rare, long-lifetime leak state during which proton flow is reversed. The probability of entering the leak state is increased at higher ΔpH. By rapidly dissipating the PMF, we propose that this leak state may enable cytochrome bo3, and possibly other HCOs, to maintain a suitable ΔpH under extreme redox conditions.
authors.affiliation: School of Biomedical Sciences, University of Leeds , LS2 9JT Leeds, U.K.
authors.forename: Mengqiu
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Chemistry, Nano-Science Center and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen , 2100 Copenhagen, Denmark.
authors.forename: Sune K
authors.initials: SK
authors.lastname: Jørgensen
authors.affiliation: School of Biomedical Sciences, University of Leeds , LS2 9JT Leeds, U.K.
authors.forename: Duncan G G
authors.initials: DG
authors.lastname: McMillan
authors.affiliation: School of Biomedical Sciences, University of Leeds , LS2 9JT Leeds, U.K.
authors.forename: Łukasz
authors.initials: Ł
authors.lastname: Krzemiński
authors.affiliation: School of Biomedical Sciences, University of Leeds , LS2 9JT Leeds, U.K.
authors.forename: Nikolaos N
authors.initials: NN
authors.lastname: Daskalakis
authors.affiliation: School of Biomedical Sciences, University of Leeds , LS2 9JT Leeds, U.K.
authors.forename: Riitta H
authors.initials: RH
authors.lastname: Partanen
authors.affiliation: Department of Chemistry, Nano-Science Center and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen , 2100 Copenhagen, Denmark.
authors.forename: Marijonas
authors.initials: M
authors.lastname: Tutkus
authors.affiliation: School of Molecular and Cellular Biology, University of Leeds , LS2 9JT Leeds, U.K.
authors.forename: Roman
authors.initials: R
authors.lastname: Tuma
authors.affiliation: Department of Chemistry, Nano-Science Center and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen , 2100 Copenhagen, Denmark.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Stamou
authors.affiliation: Department of Chemistry, Nano-Science Center and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen , 2100 Copenhagen, Denmark.
authors.forename: Nikos S
authors.initials: NS
authors.lastname: Hatzakis
authors.affiliation: School of Biomedical Sciences, University of Leeds , LS2 9JT Leeds, U.K.
authors.forename: Lars J C
authors.initials: LJ
authors.lastname: Jeuken