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Lee JW. Transient protonic capacitor: Explaining the bacteriorhodopsin membrane experiment of Heberle et al. 1994. Biophys Chem 2023; 300:107072. [PMID: 37406610 DOI: 10.1016/j.bpc.2023.107072] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 06/22/2023] [Accepted: 06/26/2023] [Indexed: 07/07/2023]
Abstract
The transmembrane-electrostatically localized protons (TELP) theory can serve as a unified framework to explain experimental observations and elucidate bioenergetic systems including both delocalized and localized protonic coupling. With the TELP model as a unified framework, it is now better explained how the bacteriorhodopsin-purple membrane-ATPase system functions. The bacteriorhodopsin pumping of protons across the membrane results in the formation of TELP around the halobacterial extracellular membrane surface that is perfectly positioned to drive ATP synthase for the synthesis of ATP from ADP and Pi. The bacteriorhodopsin purple membrane sheet experiment of Heberle et al. 1994 is now better explained here as a transient "protonic capacitor". During the lifetime of a flashlight-induced protonic bacteriorhodopsin purple membrane capacitor activity, there is at least a transient non-zero membrane potential (Δψ ≠ 0). The experimental results demonstrated that "after proton release by an integral membrane protein, long-range proton transfer along the membrane surface is faster than proton exchange with the bulk water phase" exactly as predicted by the TELP theory, which is fundamentally important to the science of bioenergetics.
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Affiliation(s)
- James Weifu Lee
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529, USA.
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2
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Ahmad R, Kleineberg C, Nasirimarekani V, Su YJ, Goli Pozveh S, Bae A, Sundmacher K, Bodenschatz E, Guido I, Vidaković-koch T, Gholami A. Light-Powered Reactivation of Flagella and Contraction of Microtubule Networks: Toward Building an Artificial Cell. ACS Synth Biol 2021; 10:1490-1504. [PMID: 33761235 PMCID: PMC8218302 DOI: 10.1021/acssynbio.1c00071] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
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Artificial systems
capable of self-sustained movement with self-sufficient
energy are of high interest with respect to the development of many
challenging applications, including medical treatments, but also technical
applications. The bottom-up assembly of such systems in the context
of synthetic biology is still a challenging task. In this work, we
demonstrate the biocompatibility and efficiency of an artificial light-driven
energy module and a motility functional unit by integrating light-switchable
photosynthetic vesicles with demembranated flagella. The flagellar
propulsion is coupled to the beating frequency, and dynamic ATP synthesis
in response to illumination allows us to control beating frequency
of flagella in a light-dependent manner. In addition, we verified
the functionality of light-powered synthetic vesicles in in
vitro motility assays by encapsulating microtubules assembled
with force-generating kinesin-1 motors and the energy module to investigate
the dynamics of a contractile filamentous network in cell-like compartments
by optical stimulation. Integration of this photosynthetic system
with various biological building blocks such as cytoskeletal filaments
and molecular motors may contribute to the bottom-up synthesis of
artificial cells that are able to undergo motor-driven morphological
deformations and exhibit directional motion in a light-controllable
fashion.
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Affiliation(s)
- Raheel Ahmad
- Max-Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
| | - Christin Kleineberg
- Max-Planck Institute for Dynamics of Complex Technical Systems, Sandtorstraße 1, 39106 Magdeburg, Germany
| | - Vahid Nasirimarekani
- Microfluidics & BIOMICS Cluster UPV/EHU, University of the Basque Country UPV/EHU, 01006 Vitoria-Gasteiz, Spain
| | - Yu-Jung Su
- Max-Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
| | - Samira Goli Pozveh
- Max-Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
| | - Albert Bae
- Department of Biomedical Engineering, University of Rochester, Rochester, New York 14627, United States
| | - Kai Sundmacher
- Max-Planck Institute for Dynamics of Complex Technical Systems, Sandtorstraße 1, 39106 Magdeburg, Germany
- Otto von Guericke University, Universitaetsplatz 2, 39106 Magdeburg, Germany
| | - Eberhard Bodenschatz
- Max-Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
- Institute for Dynamics of Complex Systems, Georg-August-University Göttingen, 37073 Göttingen, Germany
| | - Isabella Guido
- Max-Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
| | - Tanja Vidaković-koch
- Max-Planck Institute for Dynamics of Complex Technical Systems, Sandtorstraße 1, 39106 Magdeburg, Germany
| | - Azam Gholami
- Max-Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
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3
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Raschdorf O, Bonn F, Zeytuni N, Zarivach R, Becher D, Schüler D. A quantitative assessment of the membrane-integral sub-proteome of a bacterial magnetic organelle. J Proteomics 2017; 172:89-99. [PMID: 29054541 DOI: 10.1016/j.jprot.2017.10.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 10/08/2017] [Accepted: 10/10/2017] [Indexed: 11/19/2022]
Abstract
Magnetotactic bacteria produce chains of complex membrane-bound organelles that direct the biomineralization of magnetic nanoparticles and serve for magnetic field navigation. These magnetosome compartments have recently emerged as a model for studying the subcellular organization of prokaryotic organelles. Previous studies indicated the presence of specific proteins with various functions in magnetosome biosynthesis. However, the exact composition and stoichiometry of the magnetosome subproteome have remained unknown. In order to quantify and unambiguously identify all proteins specifically targeted to the magnetosome membrane of the Alphaproteobacterium Magnetospirillum gryphiswaldense, we analyzed the protein composition of several cellular fractions by semi-quantitative mass spectrometry. We found that nearly all genuine magnetosome membrane-integral proteins belong to a well-defined set of previously identified proteins encoded by gene clusters within a genomic island, indicating a highly controlled protein composition. Magnetosome proteins were present in different quantities with up to 120 copies per particle as estimated by correlating our results with available quantitative Western blot data. This high abundance suggests an unusually crowded protein composition of the membrane and a tight packing with transmembrane domains of integral proteins. Our findings will help to further define the structure of the organelle and contribute to the elucidation of magnetosome biogenesis. BIOLOGICAL SIGNIFICANCE Magnetosomes are one of the most complex bacterial organelles and consist of membrane-bounded crystals of magnetic minerals. The exact composition and stoichiometry of the associated membrane integral proteins are of major interest for a deeper understanding of prokaryotic organelle assembly; however, previous proteomic studies failed to reveal meaningful estimations due to the lack of precise and quantitative data, and the inherently high degree of accumulated protein contaminants in purified magnetosomes. Using a highly sensitive mass spectrometer, we acquired proteomic data from several cellular fractions of a magnetosome producing magnetotactic bacterium and developed a comparative algorithm to identify all genuine magnetosome membrane-integral proteins and to discriminate them from contaminants. Furthermore, by combining our data with previously published quantitative Western blot data, we were able to model the protein copy number and density within the magnetosome membrane. Our results suggest that the magnetosome membrane is specifically associated with a small subset of integral proteins that are tightly packed within the lipid layer. Our study provides by far the most comprehensive estimation of magnetosomal protein composition and stoichiometry and will help to elucidate the complex process of magnetosome biogenesis.
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Affiliation(s)
- Oliver Raschdorf
- Department of Microbiology, Ludwig Maximilian University of Munich, Germany
| | - Florian Bonn
- Department of Microbiology, Ernst Moritz Arndt University of Greifswald, Germany
| | - Natalie Zeytuni
- Department of Life Sciences, The National Institute for Biotechnology in the Negev, Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beersheba, Israel
| | - Raz Zarivach
- Department of Life Sciences, The National Institute for Biotechnology in the Negev, Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beersheba, Israel
| | - Dörte Becher
- Department of Microbiology, Ernst Moritz Arndt University of Greifswald, Germany
| | - Dirk Schüler
- Department of Microbiology, University of Bayreuth, Germany.
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4
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Talaue CO, del Rosario RCH, Pfeiffer F, Mendoza ER, Oesterhelt D. Model Construction and Analysis of Respiration in Halobacterium salinarum. PLoS One 2016; 11:e0151839. [PMID: 27011330 PMCID: PMC4806987 DOI: 10.1371/journal.pone.0151839] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 03/05/2016] [Indexed: 12/05/2022] Open
Abstract
The archaeon Halobacterium salinarum can produce energy using three different processes, namely photosynthesis, oxidative phosphorylation and fermentation of arginine, and is thus a model organism in bioenergetics. Compared to its bacteriorhodopsin-driven photosynthesis, less attention has been devoted to modeling its respiratory pathway. We created a system of ordinary differential equations that models its oxidative phosphorylation. The model consists of the electron transport chain, the ATP synthase, the potassium uniport and the sodium-proton antiport. By fitting the model parameters to experimental data, we show that the model can explain data on proton motive force generation, ATP production, and the charge balancing of ions between the sodium-proton antiporter and the potassium uniport. We performed sensitivity analysis of the model parameters to determine how the model will respond to perturbations in parameter values. The model and the parameters we derived provide a resource that can be used for analytical studies of the bioenergetics of H. salinarum.
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Affiliation(s)
- Cherryl O. Talaue
- Institute of Mathematics, University of the Philippines, Diliman, Quezon City, Philippines
| | - Ricardo C. H. del Rosario
- Institute of Mathematics, University of the Philippines, Diliman, Quezon City, Philippines
- Max Planck Institute of Biochemistry, Department of Membrane Biochemistry, Martinsried, Germany
- * E-mail:
| | - Friedhelm Pfeiffer
- Max Planck Institute of Biochemistry, Department of Membrane Biochemistry, Martinsried, Germany
| | - Eduardo R. Mendoza
- Institute of Mathematics, University of the Philippines, Diliman, Quezon City, Philippines
- Max Planck Institute of Biochemistry, Department of Membrane Biochemistry, Martinsried, Germany
| | - Dieter Oesterhelt
- Max Planck Institute of Biochemistry, Department of Membrane Biochemistry, Martinsried, Germany
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Wang T, Oppawsky C, Duan Y, Tittor J, Oesterhelt D, Facciotti MT. Stable closure of the cytoplasmic half-channel is required for efficient proton transport at physiological membrane potentials in the bacteriorhodopsin catalytic cycle. Biochemistry 2014; 53:2380-90. [PMID: 24660845 PMCID: PMC4004217 DOI: 10.1021/bi4013808] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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The bacteriorhodopsin (BR) Asp96Gly/Phe171Cys/Phe219Leu
triple
mutant has been shown to translocate protons 66% as efficiently as
the wild-type protein. Light-dependent ATP synthesis in haloarchaeal
cells expressing the triple mutant is 85% that of the wild-type BR
expressing cells. Therefore, the functional activity of BR seems to
be largely preserved in the triple mutant despite the observations
that its ground-state structure resembles that of the wild-type M
state (i.e., the so-called cytoplasmically open state) and that the
mutant shows no significant structural changes during its photocycle,
in sharp contrast to what occurs in the wild-type protein in which
a large structural opening and closing occurs on the cytoplasmic side.
To resolve the contradiction between the apparent functional robustness
of the triple mutant and the presumed importance of the opening and
closing that occurs in the wild-type protein, we conducted additional
experiments to compare the behavior of wild-type and mutant proteins
under different operational loads. Specifically, we characterized
the ability of the two proteins to generate light-driven proton currents
against a range of membrane potentials. The wild-type protein showed
maximal conductance between −150 and −50 mV, whereas
the mutant showed maximal conductance at membrane potentials >+50
mV. Molecular dynamics (MD) simulations of the triple mutant were
also conducted to characterize structural changes in the protein and
in solvent accessibility that might help to functionally contextualize
the current–voltage data. These simulations revealed that the
cytoplasmic half-channel of the triple mutant is constitutively open
and dynamically exchanges water with the bulk. Collectively, the data
and simulations help to explain why this mutant BR does not mediate
photosynthetic growth of haloarchaeal cells, and they suggest that
the structural closing observed in the wild-type protein likely plays
a key role in minimizing substrate back flow in the face of electrochemical
driving forces present at physiological membrane potentials.
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Affiliation(s)
- Ting Wang
- Department of Biomedical Engineering and Genome Center, 451 East Health Science Drive, University of California , Davis, California 95616-8816, United States
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Wang W, Geiger JH, Borhan B. The photochemical determinants of color vision: revealing how opsins tune their chromophore's absorption wavelength. Bioessays 2013; 36:65-74. [PMID: 24323922 DOI: 10.1002/bies.201300094] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The evolution of a variety of important chromophore-dependent biological processes, including microbial light sensing and mammalian color vision, relies on protein modifications that alter the spectral characteristics of a bound chromophore. Three different color opsins share the same chromophore, but have three distinct absorptions that together cover the entire visible spectrum, giving rise to trichromatic vision. The influence of opsins on the absorbance of the chromophore has been studied through methods such as model compounds, opsin mutagenesis, and computational modeling. The recent development of rhodopsin mimic that uses small soluble proteins to recapitulate the binding and wavelength tuning of the native opsins provides a new platform for studying protein-regulated spectral tuning. The ability to achieve far-red shifted absorption in the rhodopsin mimic system was attributed to a combination of the lack of a counteranion proximal to the iminium, and a uniformly neutral electrostatic environment surrounding the chromophore.
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Affiliation(s)
- Wenjing Wang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
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7
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Mechanism of voltage-sensitive fluorescence in a microbial rhodopsin. Proc Natl Acad Sci U S A 2013; 110:5939-44. [PMID: 23530193 DOI: 10.1073/pnas.1215595110] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Microbial rhodopsins were recently introduced as genetically encoded fluorescent indicators of membrane voltage. An understanding of the mechanism underlying this function would aid in the design of improved voltage indicators. We asked, what states can the protein adopt, and which states are fluorescent? How does membrane voltage affect the photostationary distribution of states? Here, we present a detailed spectroscopic characterization of Archaerhodopsin 3 (Arch). We performed fluorescence spectroscopy on Arch and its photogenerated intermediates in Escherichia coli and in single HEK293 cells under voltage-clamp conditions. These experiments probed the effects of time-dependent illumination and membrane voltage on absorption, fluorescence, membrane current, and membrane capacitance. The fluorescence of Arch arises through a sequential three-photon process. Membrane voltage modulates protonation of the Schiff base in a 13-cis photocycle intermediate (M ⇌ N equilibrium), not in the ground state as previously hypothesized. We present experimental protocols for optimized voltage imaging with Arch, and we discuss strategies for engineering improved rhodopsin-based voltage indicators.
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