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Li M, Khan S, Rong H, Tuma R, Hatzakis NS, Jeuken LJC. Effects of membrane curvature and pH on proton pumping activity of single cytochrome bo 3 enzymes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017. [PMID: 28634030 DOI: 10.1016/j.bbabio.2017.06.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The molecular mechanism of proton pumping by heme-copper oxidases (HCO) has intrigued the scientific community since it was first proposed. We have recently reported a novel technology that enables the continuous characterisation of proton transport activity of a HCO and ubiquinol oxidase from Escherichia coli, cytochrome bo3, for hundreds of seconds on the single enzyme level (Li et al. J Am Chem Soc 137 (2015) 16055-16063). Here, we have extended these studies by additional experiments and analyses of the proton transfer rate as a function of proteoliposome size and pH at the N- and P-side of single HCOs. Proton transport activity of cytochrome bo3 was found to decrease with increased curvature of the membrane. Furthermore, proton uptake at the N-side (proton entrance) was insensitive to pH between pH6.4-8.4, while proton release at the P-side had an optimum pH of ~7.4, suggesting that the pH optimum is related to proton release from the proton exit site. Our previous single-enzyme experiments identified rare, long-lived conformation states of cytochrome bo3 where protons leak back under turn-over conditions. Here, we analyzed and found that ~23% of cytochrome bo3 proteoliposomes show ΔpH half-lives below 50s after stopping turnover, while only ~5% of the proteoliposomes containing a non-pumping mutant, E286C cytochrome bo3 exhibit such fast decays. These single-enzyme results confirm our model in which HCO exhibit heterogeneous pumping rates and can adopt rare leak states in which protons are able to rapidly flow back.
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Affiliation(s)
- Mengqiu Li
- School of Biomedical Sciences, University of Leeds, LS2 9JT Leeds, UK
| | - Sanobar Khan
- School of Chemistry, University of Leeds, LS2 9JT Leeds, UK
| | - Honglin Rong
- School of Biomedical Sciences, University of Leeds, LS2 9JT Leeds, UK
| | - Roman Tuma
- School of Molecular and Cellular Biology, University of Leeds, LS2 9JT Leeds, UK
| | - Nikos S Hatzakis
- Nano-Science Center, Department of Chemistry, University of Copenhagen, Copenhagen 2100, Denmark.
| | - Lars J C Jeuken
- School of Biomedical Sciences, University of Leeds, LS2 9JT Leeds, UK.
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Li M, Jørgensen SK, McMillan DGG, Krzemiński Ł, Daskalakis NN, Partanen RH, Tutkus M, Tuma R, Stamou D, Hatzakis NS, Jeuken LJC. Single Enzyme Experiments Reveal a Long-Lifetime Proton Leak State in a Heme-Copper Oxidase. J Am Chem Soc 2015; 137:16055-63. [PMID: 26618221 PMCID: PMC4697922 DOI: 10.1021/jacs.5b08798] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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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.
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Affiliation(s)
- Mengqiu Li
- School of Biomedical Sciences, University of Leeds , LS2 9JT Leeds, U.K
| | - Sune K Jørgensen
- Department of Chemistry, Nano-Science Center and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen , 2100 Copenhagen, Denmark
| | | | - Łukasz Krzemiński
- School of Biomedical Sciences, University of Leeds , LS2 9JT Leeds, U.K
| | | | - Riitta H Partanen
- School of Biomedical Sciences, University of Leeds , LS2 9JT Leeds, U.K
| | - Marijonas Tutkus
- Department of Chemistry, Nano-Science Center and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen , 2100 Copenhagen, Denmark
| | - Roman Tuma
- School of Molecular and Cellular Biology, University of Leeds , LS2 9JT Leeds, U.K
| | - Dimitrios Stamou
- Department of Chemistry, Nano-Science Center and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen , 2100 Copenhagen, Denmark
| | - Nikos S Hatzakis
- Department of Chemistry, Nano-Science Center and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen , 2100 Copenhagen, Denmark
| | - Lars J C Jeuken
- School of Biomedical Sciences, University of Leeds , LS2 9JT Leeds, U.K
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