1
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Nie X, You W, Zhang Z, Gao F, Zhou XH, Wang HL, Wang LH, Chen G, Wang CH, Hong CY, Shao Q, Wang F, Xia L, Li Y, You YZ. DPA-Zinc around Polyplexes Acts Like PEG to Reduce Protein Binding While Targeting Cancer Cells. Adv Healthc Mater 2023; 12:e2203252. [PMID: 37154112 DOI: 10.1002/adhm.202203252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 04/24/2023] [Indexed: 05/10/2023]
Abstract
Gene therapy holds great promise as an effective treatment for many diseases of genetic origin. Gene therapy works by employing cationic polymers, liposomes, and nanoparticles to condense DNA into polyplexes via electronic interactions. Then, a therapeutic gene is introduced into target cells, thereby restoring or changing cellular function. However, gene transfection efficiency remains low in vivo due to high protein binding, poor targeting ability, and substantial endosomal entrapment. Artificial sheaths containing PEG, anions, or zwitterions can be introduced onto the surface of gene carriers to prevent interaction with proteins; however, they reduce the cellular uptake efficacy, endosomal escape, targeting ability, thereby, lowering gene transfection. Here, it is reported that linking dipicolylamine-zinc (DPA-Zn) ions onto polyplex nanoparticles can produce a strong hydration water layer around the polyplex, mimicking the function of PEGylation to reduce protein binding while targeting cancer cells, augmenting cellular uptake and endosomal escape. The polyplexes with a strong hydration water layer on the surface can achieve a high gene transfection even in a 50% serum environment. This strategy provides a new solution for preventing protein adsorption while improving cellular uptake and endosomal escape.
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Affiliation(s)
- Xuan Nie
- Department of Pharmacy, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Wei You
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Ze Zhang
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Fan Gao
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Xiao-Hong Zhou
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Hai-Li Wang
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Long-Hai Wang
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Guang Chen
- Department of Pharmacy, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Chang-Hui Wang
- Department of Cardiology, The First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, 230022, China
| | - Chun-Yan Hong
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Qi Shao
- Department of Pharmacy, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Fei Wang
- Department of Neurosurgery, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Lei Xia
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, 230026, China
| | - Yang Li
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | - Ye-Zi You
- Department of Pharmacy, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, 230026, China
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2
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Brünig FN, Hillmann P, Kim WK, Daldrop JO, Netz RR. Proton-transfer spectroscopy beyond the normal-mode scenario. J Chem Phys 2022; 157:174116. [DOI: 10.1063/5.0116686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
A stochastic theory is developed to predict the spectral signature of proton-transfer processes and is applied to infrared spectra computed from ab initio molecular-dynamics simulations of a single [Formula: see text] cation. By constraining the oxygen atoms to a fixed distance, this system serves as a tunable model for general proton-transfer processes with variable barrier height. Three spectral contributions at distinct frequencies are identified and analytically predicted: the quasi-harmonic motion around the most probable configuration, amenable to normal-mode analysis, the contribution due to transfer paths when the proton moves over the barrier, and a shoulder for low frequencies stemming from the stochastic transfer-waiting-time distribution; the latter two contributions are not captured by normal-mode analysis but exclusively reported on the proton-transfer kinetics. In accordance with reaction rate theory, the transfer-waiting-contribution frequency depends inversely exponentially on the barrier height, whereas the transfer-path-contribution frequency is rather insensitive to the barrier height.
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Affiliation(s)
- Florian N. Brünig
- Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Paul Hillmann
- Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Won Kyu Kim
- School of Computational Sciences, Korea Institute for Advanced Study, Seoul 02455, Republic of Korea
| | - Jan O. Daldrop
- Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Roland R. Netz
- Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
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Protons in Gating the Kv1.2 Channel: A Calculated Set of Protonation States in Response to Polarization/Depolarization of the Channel, with the Complete Proposed Proton Path from Voltage Sensing Domain to Gate. MEMBRANES 2022; 12:membranes12070718. [PMID: 35877921 PMCID: PMC9318985 DOI: 10.3390/membranes12070718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 07/07/2022] [Accepted: 07/08/2022] [Indexed: 12/04/2022]
Abstract
We have in the past proposed that proton motion constitutes the gating current in the potassium channel Kv1.2 and is responsible for the gating mechanism. For this to happen, there must be a proton path between the voltage-sensing domain (VSD) and the channel gate, and here we present quantum calculations that lead to a specific pair of proton paths, defined at the molecular level, with well-defined water molecule linkages, and with hydrogen bonding between residues; there is also at least one interpath crossover, where protons can switch paths. Quantum calculations on the entire 563-atom system give the complete geometry, the energy, and atomic charges. Calculations show that three specific residues (in the pdb 3Lut numbering, H418, E327, R326), and the T1 intracellular moiety, all of which have been shown experimentally to be involved in gating, would necessarily be protonated or deprotonated in the path between the VSD and the gate. Hydroxyl reorientation of serine and threonine residues are shown to provide a means of adjusting proton directions of motion. In the deprotonated state for K312, a low energy state, our calculations come close to reproducing the X-ray structure. The demonstration of the existence of a double proton path between VSD and gate supports the proposed proton gating mechanism; when combined with our earlier demonstration of proton generation in the VSD, and comparison with other systems that are known to move protons, we are close to achieving the definition of a complete gating mechanism in molecular detail. The coupling of the paths to the VSD, and to the PVPV section that essentially forms the gate, can be easily seen from the results of the calculation. The gate itself remains for further computations.
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4
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Dynamic Coupling of Tyrosine 185 with the Bacteriorhodopsin Photocycle, as Revealed by Chemical Shifts, Assisted AF-QM/MM Calculations and Molecular Dynamic Simulations. Int J Mol Sci 2021; 22:ijms222413587. [PMID: 34948384 PMCID: PMC8709120 DOI: 10.3390/ijms222413587] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 12/14/2021] [Accepted: 12/16/2021] [Indexed: 11/23/2022] Open
Abstract
Aromatic residues are highly conserved in microbial photoreceptors and play crucial roles in the dynamic regulation of receptor functions. However, little is known about the dynamic mechanism of the functional role of those highly conserved aromatic residues during the receptor photocycle. Tyrosine 185 (Y185) is one of the highly conserved aromatic residues within the retinal binding pocket of bacteriorhodopsin (bR). In this study, we explored the molecular mechanism of its dynamic coupling with the bR photocycle by automated fragmentation quantum mechanics/molecular mechanics (AF-QM/MM) calculations and molecular dynamic (MD) simulations based on chemical shifts obtained by 2D solid-state NMR correlation experiments. We observed that Y185 plays a significant role in regulating the retinal cis–trans thermal equilibrium, stabilizing the pentagonal H-bond network, participating in the orientation switch of Schiff Base (SB) nitrogen, and opening the F42 gate by interacting with the retinal and several key residues along the proton translocation channel. Our findings provide a detailed molecular mechanism of the dynamic couplings of Y185 and the bR photocycle from a structural perspective. The method used in this paper may be applied to the study of other microbial photoreceptors.
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Nakai H, Takemura T, Ono J, Nishimura Y. Quantum-Mechanical Molecular Dynamics Simulations on Secondary Proton Transfer in Bacteriorhodopsin Using Realistic Models. J Phys Chem B 2021; 125:10947-10963. [PMID: 34582194 DOI: 10.1021/acs.jpcb.1c06231] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Bacteriorhodopsin (BR) transports a proton from intracellular to extracellular (EC) sites through five proton transfers. The second proton transfer is the release of an excess proton stored in BR into the EC medium, and an atomistic understanding of this whole process has remained unexplored due to its ubiquitous environment. Here, fully quantum mechanical (QM) molecular dynamics (MD) and metadynamics (MTD) simulations for this process were performed at the divide-and-conquer density-functional tight-binding level using realistic models (∼50000 and ∼20000 atoms) based on the time-resolved photointermediate structures from an X-ray free electron laser. Regarding the proton storage process, the QM-MD/MTD simulations confirmed the Glu-shared mechanism, in which an excess proton is stored between Glu194 and Glu204, and clarified that the activation occurs by localizing the proton at Glu204 in the photocycle. Furthermore, the QM-MD/MTD simulations elucidated a release pathway from Glu204 through Ser193 to the EC water molecules and clarified that the proton release starts at ∼250 μs. In the ubiquitous proton diffusion in the EC medium, the transient proton receptors predicted experimentally were assigned to carboxylates in Glu9 and Glu74. Large-scale QM-MD/MTD simulations beyond the conventional sizes, which provided the above findings and confirmations, were possible by adopting our Dcdftbmd program.
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Affiliation(s)
- Hiromi Nakai
- Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan.,Waseda Research Institute for Science and Engineering (WISE), Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan.,Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University, 1-30 Goryo-Ohara, Nishikyo-ku, Kyoto 615-8245, Japan
| | - Toshiaki Takemura
- Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan
| | - Junichi Ono
- Waseda Research Institute for Science and Engineering (WISE), Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan.,Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University, 1-30 Goryo-Ohara, Nishikyo-ku, Kyoto 615-8245, Japan
| | - Yoshifumi Nishimura
- Waseda Research Institute for Science and Engineering (WISE), Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan
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6
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Maag D, Mast T, Elstner M, Cui Q, Kubař T. O to bR transition in bacteriorhodopsin occurs through a proton hole mechanism. Proc Natl Acad Sci U S A 2021; 118:e2024803118. [PMID: 34561302 PMCID: PMC8488608 DOI: 10.1073/pnas.2024803118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2021] [Indexed: 12/27/2022] Open
Abstract
Extensive classical and quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulations are used to establish the structural features of the O state in bacteriorhodopsin (bR) and its conversion back to the bR ground state. The computed free energy surface is consistent with available experimental data for the kinetics and thermodynamics of the O to bR transition. The simulation results highlight the importance of the proton release group (PRG, consisting of Glu194/204) and the conserved arginine 82 in modulating the hydration level of the protein cavity. In particular, in the O state, deprotonation of the PRG and downward rotation of Arg82 lead to elevated hydration level and a continuous water network that connects the PRG to the protonated Asp85. Proton exchange through this water network is shown by ∼0.1-μs semiempirical QM/MM free energy simulations to occur through the generation and propagation of a proton hole, which is relayed by Asp212 and stabilized by Arg82. This mechanism provides an explanation for the observation that the D85S mutant of bacteriorhodopsin pumps chloride ions. The electrostatics-hydration coupling mechanism and the involvement of all titration states of water are likely applicable to many biomolecules involved in bioenergetic transduction.
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Affiliation(s)
- Denis Maag
- Institute of Physical Chemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Thilo Mast
- Institute of Physical Chemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Marcus Elstner
- Institute of Physical Chemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
- Institute for Biological Interfaces, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Qiang Cui
- Department of Chemistry, Boston University, Boston, MA 02215
- Department of Physics, Boston University, Boston, MA 02215
- Department of Biomedical Engineering, Boston University, Boston, MA 02215
| | - Tomáš Kubař
- Institute of Physical Chemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany;
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7
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Ono J, Imai M, Nishimura Y, Nakai H. Hydroxide Ion Carrier for Proton Pumps in Bacteriorhodopsin: Primary Proton Transfer. J Phys Chem B 2020; 124:8524-8539. [DOI: 10.1021/acs.jpcb.0c05507] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Junichi Ono
- Waseda Research Institute for Science and Engineering (WISE), Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan
- Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University, 1-30 Goryo-Ohara, Nishikyo-ku, Kyoto 615-8245, Japan
| | - Minori Imai
- Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan
| | - Yoshifumi Nishimura
- Waseda Research Institute for Science and Engineering (WISE), Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan
| | - Hiromi Nakai
- Waseda Research Institute for Science and Engineering (WISE), Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan
- Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University, 1-30 Goryo-Ohara, Nishikyo-ku, Kyoto 615-8245, Japan
- Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan
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8
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Zhong H, Wu G, Fu Z, Lv H, Xu G, Wang R. Flexible Porous Organic Polymer Membranes for Protonic Field-Effect Transistors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2000730. [PMID: 32301209 DOI: 10.1002/adma.202000730] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2020] [Revised: 03/06/2020] [Accepted: 03/23/2020] [Indexed: 06/11/2023]
Abstract
Artificial transistors represent an ideal means for meeting the requirements in interfacing with biological systems. It is pivotal to develop new proton-conductive materials for the transduction between biochemical events and electronic signals. Herein, the first demonstration of a porous organic polymer membrane (POPM) as a proton-conductive material for protonic field-effect transistors is presented. The POPM is readily prepared through a thiourea-formation condensation reaction. Under hydrated conditions and at room temperature, the POPM delivers a proton mobility of 5.7 × 10-3 cm2 V-1 s-1 ; the charge carrier densities are successfully modulated from 4.3 × 1017 to 14.1 × 1017 cm-3 by the gate voltage. This study provides a type of promising modular proton-conductive materials for bioelectronics application.
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Affiliation(s)
- Hong Zhong
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Guodong Wu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
| | - Zhihua Fu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
| | - Haowei Lv
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
| | - Gang Xu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ruihu Wang
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
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9
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Palese LL. Oxygen-oxygen distances in protein-bound crystallographic water suggest the presence of protonated clusters. Biochim Biophys Acta Gen Subj 2020; 1864:129480. [DOI: 10.1016/j.bbagen.2019.129480] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 10/27/2019] [Accepted: 10/28/2019] [Indexed: 12/11/2022]
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10
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Tripathi R, Forbert H, Marx D. Settling the Long-Standing Debate on the Proton Storage Site of the Prototype Light-Driven Proton Pump Bacteriorhodopsin. J Phys Chem B 2019; 123:9598-9608. [DOI: 10.1021/acs.jpcb.9b09608] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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11
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Branda MM, Guérin DMA. Alkalinization of Icosahedral Non-enveloped Viral Capsid Interior Through Proton Channeling. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1215:181-199. [DOI: 10.1007/978-3-030-14741-9_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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12
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Viso JF, Belelli P, Machado M, González H, Pantano S, Amundarain MJ, Zamarreño F, Branda MM, Guérin DMA, Costabel MD. Multiscale modelization in a small virus: Mechanism of proton channeling and its role in triggering capsid disassembly. PLoS Comput Biol 2018; 14:e1006082. [PMID: 29659564 PMCID: PMC5919690 DOI: 10.1371/journal.pcbi.1006082] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 04/26/2018] [Accepted: 03/09/2018] [Indexed: 12/04/2022] Open
Abstract
In this work, we assess a previously advanced hypothesis that predicts the existence of ion channels in the capsid of small and non-enveloped icosahedral viruses. With this purpose we examine Triatoma Virus (TrV) as a case study. This virus has a stable capsid under highly acidic conditions but disassembles and releases the genome in alkaline environments. Our calculations range from a subtle sub-atomic proton interchange to the dismantling of a large-scale system representing several million of atoms. Our results provide structure-based explanations for the three roles played by the capsid to enable genome release. First, we observe, for the first time, the formation of a hydrophobic gate in the cavity along the five-fold axis of the wild-type virus capsid, which can be disrupted by an ion located in the pore. Second, the channel enables protons to permeate the capsid through a unidirectional Grotthuss-like mechanism, which is the most likely process through which the capsid senses pH. Finally, assuming that the proton leak promotes a charge imbalance in the interior of the capsid, we model an internal pressure that forces shell cracking using coarse-grained simulations. Although qualitatively, this last step could represent the mechanism of capsid opening that allows RNA release. All of our calculations are in agreement with current experimental data obtained using TrV and describe a cascade of events that could explain the destabilization and disassembly of similar icosahedral viruses. Plant and animal small non-enveloped viruses are composed of a capsid shell that encloses the genome. One of the multiple functions played by the capsid is to protect the genome against host defenses and to withstand environmental aggressions, such as dehydration. This highly specialized capsule selectively recognizes and binds to the target tissue infected by the virus. In the viral cycle, the ultimate function of the capsid is to release the genome. Observations of many viruses demonstrate that the pH of the medium can trigger genome release. Nevertheless, the mechanism underlying this process at the atomic level is poorly understood. In this work, we computationally modeled the mechanism by which the capsid senses environmental pH and the destabilization process that permits genome release. Our calculations predict that a cavity that traverses the capsid functions as a hydrophobic gate, a feature already observed in membrane ion channels. Moreover, our results predict that this cavity behaves as a proton diode because the proton transit can only occur from the capsid interior to the exterior. In turn, our calculations describe a cascade of events that could explain the destabilization and dismantling of an insect virus, but this description could also apply to many vertebrate viruses.
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Affiliation(s)
- Juan Francisco Viso
- Departamento de Física (DF), Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina
- DF-UNS, Grupo de Biofísica, Instituto de Física del Sur (IFISUR, UNS/CONICET), Bahía Blanca, Argentina
| | - Patricia Belelli
- DF-UNS, Grupo de Materiales y Sistemas Catalíticos (GRUMASICA), IFISUR, Bahía Blanca, Argentina
| | - Matías Machado
- Grupo de Simulaciones Biomoleculares, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Humberto González
- Grupo de Simulaciones Biomoleculares, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Sergio Pantano
- Grupo de Simulaciones Biomoleculares, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - María Julia Amundarain
- Departamento de Física (DF), Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina
- DF-UNS, Grupo de Biofísica, Instituto de Física del Sur (IFISUR, UNS/CONICET), Bahía Blanca, Argentina
| | - Fernando Zamarreño
- Departamento de Física (DF), Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina
- DF-UNS, Grupo de Biofísica, Instituto de Física del Sur (IFISUR, UNS/CONICET), Bahía Blanca, Argentina
| | - Maria Marta Branda
- Departamento de Física (DF), Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina
- DF-UNS, Grupo de Materiales y Sistemas Catalíticos (GRUMASICA), IFISUR, Bahía Blanca, Argentina
| | - Diego M. A. Guérin
- Instituto Biofisika (UPV/EHU, CSIC), Department of Biochemistry and Molecular Biology, University of the Basque Country (EHU), Barrio Sarriena S/N, Leioa, Vizcaya, Spain
- * E-mail: (MDC); (DMAG)
| | - Marcelo D. Costabel
- Departamento de Física (DF), Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina
- DF-UNS, Grupo de Biofísica, Instituto de Física del Sur (IFISUR, UNS/CONICET), Bahía Blanca, Argentina
- * E-mail: (MDC); (DMAG)
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13
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Volkov O, Kovalev K, Polovinkin V, Borshchevskiy V, Bamann C, Astashkin R, Marin E, Popov A, Balandin T, Willbold D, Büldt G, Bamberg E, Gordeliy V. Structural insights into ion conduction by channelrhodopsin 2. Science 2018; 358:358/6366/eaan8862. [PMID: 29170206 DOI: 10.1126/science.aan8862] [Citation(s) in RCA: 119] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 10/30/2017] [Indexed: 11/02/2022]
Abstract
The light-gated ion channel channelrhodopsin 2 (ChR2) from Chlamydomonas reinhardtii is a major optogenetic tool. Photon absorption starts a well-characterized photocycle, but the structural basis for the regulation of channel opening remains unclear. We present high-resolution structures of ChR2 and the C128T mutant, which has a markedly increased open-state lifetime. The structure reveals two cavities on the intracellular side and two cavities on the extracellular side. They are connected by extended hydrogen-bonding networks involving water molecules and side-chain residues. Central is the retinal Schiff base that controls and synchronizes three gates that separate the cavities. Separate from this network is the DC gate that comprises a water-mediated bond between C128 and D156 and interacts directly with the retinal Schiff base. Comparison with the C128T structure reveals a direct connection of the DC gate to the central gate and suggests how the gating mechanism is affected by subtle tuning of the Schiff base's interactions.
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Affiliation(s)
- Oleksandr Volkov
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Juelich, Juelich, Germany
| | - Kirill Kovalev
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Juelich, Juelich, Germany.,Institut de Biologie Structurale Jean-Pierre Ebel, Université Grenoble Alpes-Commissariat à l'Energie Atomique et aux Energies Alternatives-CNRS, Grenoble, France.,Moscow Institute of Physics and Technology, Dolgoprudny, Russia.,Institute of Crystallography, University of Aachen, Aachen, Germany
| | - Vitaly Polovinkin
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Juelich, Juelich, Germany.,Institut de Biologie Structurale Jean-Pierre Ebel, Université Grenoble Alpes-Commissariat à l'Energie Atomique et aux Energies Alternatives-CNRS, Grenoble, France.,Moscow Institute of Physics and Technology, Dolgoprudny, Russia.,ELI Beamlines, Institute of Physics, Czech Academy of Sciences, 18221 Prague, Czech Republic
| | | | | | - Roman Astashkin
- Institut de Biologie Structurale Jean-Pierre Ebel, Université Grenoble Alpes-Commissariat à l'Energie Atomique et aux Energies Alternatives-CNRS, Grenoble, France.,Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Egor Marin
- Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Alexander Popov
- European Synchrotron Radiation Facility, 38027 Grenoble, France
| | - Taras Balandin
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Juelich, Juelich, Germany
| | - Dieter Willbold
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Juelich, Juelich, Germany.,Institut de Biologie Structurale Jean-Pierre Ebel, Université Grenoble Alpes-Commissariat à l'Energie Atomique et aux Energies Alternatives-CNRS, Grenoble, France.,Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Georg Büldt
- Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Ernst Bamberg
- Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
| | - Valentin Gordeliy
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Juelich, Juelich, Germany. .,Institut de Biologie Structurale Jean-Pierre Ebel, Université Grenoble Alpes-Commissariat à l'Energie Atomique et aux Energies Alternatives-CNRS, Grenoble, France.,Moscow Institute of Physics and Technology, Dolgoprudny, Russia
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14
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Ghane T, Gorriz RF, Wrzalek S, Volkenandt S, Dalatieh F, Reidelbach M, Imhof P. Hydrogen-Bonded Network and Water Dynamics in the D-channel of Cytochrome c Oxidase. J Membr Biol 2018; 251:299-314. [PMID: 29435610 DOI: 10.1007/s00232-018-0019-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 02/06/2018] [Indexed: 01/09/2023]
Abstract
Proton transfer in cytochrome c oxidase (CcO) from the cellular inside to the binuclear redox centre as well as proton pumping through the membrane takes place through proton entrance via two distinct pathways, the D- and K-channel. Both channels show a dependence of their hydration level on the protonation states of their key residues, K362 for the K-channel, and E286 or D132 for the D-channel. In the oxidative half of CcO's catalytic cycle the D-channel is the proton-conducting path. For this channel, an interplay of protonation state of the D-channel residues with the water and hydrogen-bond dynamics has been observed in molecular dynamics simulations of the CcO protein, embedded in a lipid bi-layer, modelled in different protonation states. Protonation of residue E286 at the end of the D-channel results in a hydrogen-bonded network pointing from E286 to N139, that is against proton transport, and favouring N139 conformations which correspond to a closed asparagine gate (formed by residues N121 and N139). Consequently, the hydration level is lower than with unprotonated E286. In those models, the Asn gate is predominantly open, allowing water molecules to pass and thus increase the hydration level. The hydrogen-bonded network in these states exhibits longer life times of the Asn residues with water than other models and shows the D-channel to be traversable from the entrance, D132, to exit, E286. The D-channel can thus be regarded as auto-regulated with respect to proton transport, allowing proton passage only when required, that is the proton is located at the lower part of the D-channel (D132 to Asn gate) and not at the exit (E286).
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Affiliation(s)
- Tahereh Ghane
- Institute of Theoretical Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Rene F Gorriz
- Institute of Theoretical Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Sandro Wrzalek
- Institute of Theoretical Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Senta Volkenandt
- Institute of Theoretical Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Ferand Dalatieh
- Institute of Theoretical Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany.,R Institute GmbH, Dortustraße 48, 14467, Potsdam, Germany
| | - Marco Reidelbach
- Institute of Theoretical Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Petra Imhof
- Institute of Theoretical Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany.
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15
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pH-sensitive vibrational probe reveals a cytoplasmic protonated cluster in bacteriorhodopsin. Proc Natl Acad Sci U S A 2017; 114:E10909-E10918. [PMID: 29203649 DOI: 10.1073/pnas.1707993114] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Infrared spectroscopy has been used in the past to probe the dynamics of internal proton transfer reactions taking place during the functional mechanism of proteins but has remained mostly silent to protonation changes in the aqueous medium. Here, by selectively monitoring vibrational changes of buffer molecules with a temporal resolution of 6 µs, we have traced proton release and uptake events in the light-driven proton-pump bacteriorhodopsin and correlate these to other molecular processes within the protein. We demonstrate that two distinct chemical entities contribute to the temporal evolution and spectral shape of the continuum band, an unusually broad band extending from 2,300 to well below 1,700 cm-1 The first contribution corresponds to deprotonation of the proton release complex (PRC), a complex in the extracellular domain of bacteriorhodopsin where an excess proton is shared by a cluster of internal water molecules and/or ionic E194/E204 carboxylic groups. We assign the second component of the continuum band to the proton uptake complex, a cluster with an excess proton reminiscent to the PRC but located in the cytoplasmic domain and possibly stabilized by D38. Our findings refine the current interpretation of the continuum band and call for a reevaluation of the last proton transfer steps in bacteriorhodopsin.
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16
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Electrogenic steps of light-driven proton transport in ESR, a retinal protein from Exiguobacterium sibiricum. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1741-1750. [DOI: 10.1016/j.bbabio.2016.08.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 08/06/2016] [Accepted: 08/11/2016] [Indexed: 02/01/2023]
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17
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Feng J, Mertz B. Proteorhodopsin Activation Is Modulated by Dynamic Changes in Internal Hydration. Biochemistry 2015; 54:7132-41. [PMID: 26562497 DOI: 10.1021/acs.biochem.5b00932] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Proteorhodopsin, a member of the microbial rhodopsin family, is a seven-transmembrane α-helical protein that functions as a light-driven proton pump. Understanding the proton-pumping mechanism of proteorhodopsin requires intimate knowledge of the proton transfer pathway via complex hydrogen-bonding networks formed by amino acid residues and internal water molecules. Here we conducted a series of microsecond time scale molecular dynamics simulations on both the dark state and the initial photoactivated state of blue proteorhodopsin to reveal the structural basis for proton transfer with respect to protein internal hydration. A complex series of dynamic hydrogen-bonding networks involving water molecules exists, facilitated by water channels and hydration sites within proteorhodopsin. High levels of hydration were discovered at each proton transfer site-the retinal binding pocket and proton uptake and release sites-underscoring the critical participation of water molecules in the proton-pumping mechanism. Water-bridged interactions and local water channels were also observed and can potentially mediate long-distance proton transfer between each site. The most significant phenomenon is after isomerization of retinal, an increase in water flux occurs that connects the proton release group, a conserved arginine residue, and the retinal binding pocket. Our results provide a detailed description of the internal hydration of the early photointermediates in the proteorhodopsin photocycle under alkaline pH conditions. These results lay the fundamental groundwork for understanding the intimate role that hydration plays in the structure-function relationship underlying the proteorhodopsin proton-pumping mechanism, as well as providing context for the relationship of hydration in proteorhodopsin to other microbial retinal proteins.
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Affiliation(s)
- Jun Feng
- The C. Eugene Bennett Department of Chemistry, West Virginia University , 217 Clark Hall, Morgantown, West Virginia 26506, United States
| | - Blake Mertz
- The C. Eugene Bennett Department of Chemistry, West Virginia University , 217 Clark Hall, Morgantown, West Virginia 26506, United States
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18
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Conversion of a light-driven proton pump into a light-gated ion channel. Sci Rep 2015; 5:16450. [PMID: 26597707 PMCID: PMC4657025 DOI: 10.1038/srep16450] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 10/14/2015] [Indexed: 12/19/2022] Open
Abstract
Interest in microbial rhodopsins with ion pumping activity has been revitalized in the context of optogenetics, where light-driven ion pumps are used for cell hyperpolarization and voltage sensing. We identified an opsin-encoding gene (CsR) in the genome of the arctic alga Coccomyxa subellipsoidea C-169 that can produce large photocurrents in Xenopus oocytes. We used this property to analyze the function of individual residues in proton pumping. Modification of the highly conserved proton shuttling residue R83 or its interaction partner Y57 strongly reduced pumping power. Moreover, this mutation converted CsR at moderate electrochemical load into an operational proton channel with inward or outward rectification depending on the amino acid substitution. Together with molecular dynamics simulations, these data demonstrate that CsR-R83 and its interacting partner Y57 in conjunction with water molecules forms a proton shuttle that blocks passive proton flux during the dark-state but promotes proton movement uphill upon illumination.
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19
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Wolf S, Freier E, Gerwert K. A delocalized proton-binding site within a membrane protein. Biophys J 2015; 107:174-84. [PMID: 24988352 DOI: 10.1016/j.bpj.2014.05.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 05/13/2014] [Accepted: 05/14/2014] [Indexed: 11/26/2022] Open
Abstract
The role of protein-bound water molecules in protein function and catalysis is an emerging topic. Here, we studied the solvation of an excess proton by protein-bound water molecules and the contribution of the surrounding amino acid residues at the proton release site of the membrane protein bacteriorhodopsin. It hosts an excess proton within a protein-bound water cluster, which is hydrogen bonded to several surrounding amino acids. Indicative of delocalization is a broad continuum absorbance experimentally observed by time-resolved Fourier transform infrared spectroscopy. In combination with site-directed mutagenesis, the involvement of several amino acids (especially Glu-194 and Glu-204) in the delocalization was elaborated. Details regarding the contributions of the glutamates and water molecules to the delocalization mode in biomolecular simulations are controversial. We carried out quantum mechanics/molecular mechanics (QM/MM) self-consistent charge density functional tight-binding simulations for all amino acids that have been experimentally shown to be involved in solvation of the excess proton, and systematically investigated the influence of the quantum box size. We compared calculated theoretical infrared spectra with experimental ones as a measure for the correct description of excess proton delocalization. A continuum absorbance can only be observed for small quantum boxes containing few amino acids and/or water molecules. Larger quantum boxes, including all experimentally shown involved amino acids, resulted in narrow absorbance bands, indicating protonation of a single binding site in contradiction to experimental results. We conclude that small quantum boxes seem to reproduce representative extreme cases of proton delocalization modes: proton delocalization only on water molecules or only between Glu-194 and Glu-204. Extending the experimental spectral region to lower wave numbers, a water-delocalized proton reproduces the observed continuum absorbance better than a glutamate-shared delocalized proton. However, a full agreement between QM simulations and experimental results on the delocalized excess proton will require a larger quantum box as well as more sophisticated QM/MM methods.
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Affiliation(s)
- Steffen Wolf
- Department of Biophysics, Chinese Academy of Sciences-Max-Planck-Gesellschaft Partner Institute for Computational Biology, Shanghai Institutes for Biological Sciences, Shanghai, P.R. China
| | - Erik Freier
- Department of Biophysics, University of Bochum, Bochum, Germany
| | - Klaus Gerwert
- Department of Biophysics, Chinese Academy of Sciences-Max-Planck-Gesellschaft Partner Institute for Computational Biology, Shanghai Institutes for Biological Sciences, Shanghai, P.R. China; Department of Biophysics, University of Bochum, Bochum, Germany.
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20
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Wolf S, Freier E, Cui Q, Gerwert K. Infrared spectral marker bands characterizing a transient water wire inside a hydrophobic membrane protein. J Chem Phys 2015; 141:22D524. [PMID: 25494795 DOI: 10.1063/1.4902237] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Proton conduction along protein-bound "water wires" is an essential feature in membrane proteins. Here, we analyze in detail a transient water wire, which conducts protons via a hydrophobic barrier within a membrane protein to create a proton gradient. It is formed only for a millisecond out of three water molecules distributed at inactive positions in a polar environment in the ground state. The movement into a hydrophobic environment causes characteristic shifts of the water bands reflecting their different chemical properties. These band shifts are identified by time-resolved Fourier Transform Infrared difference spectroscopy and analyzed by biomolecular Quantum Mechanical/Molecular Mechanical simulations. A non-hydrogen bonded ("dangling") O-H stretching vibration band and a broad continuum absorbance caused by a combined vibration along the water wire are identified as characteristic marker bands of such water wires in a hydrophobic environment. The results provide a basic understanding of water wires in hydrophobic environments.
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Affiliation(s)
- Steffen Wolf
- Department of Biophysics, Ruhr-University Bochum, Universitätsstraße 150, 44780 Bochum, Germany
| | - Erik Freier
- Department of Biophysics, Chinese Academy of Sciences, Max-Planck-Gesellschaft Partner Institute for Computational Biology, 320 Yue Yang Road, 200031 Shanghai, China
| | - Qiang Cui
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin, Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA
| | - Klaus Gerwert
- Department of Biophysics, Ruhr-University Bochum, Universitätsstraße 150, 44780 Bochum, Germany
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21
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Rao S, Guo Z, Liang D, Chen D, Li Y, Xiang Y. 3D proton transfer augments bio-photocurrent generation. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:2668-2673. [PMID: 25786358 DOI: 10.1002/adma.201405737] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 02/14/2015] [Indexed: 06/04/2023]
Abstract
An enhancement of the photocurrent is achieved in a biohybrid nanocomposite consisting of nanovesicle reconstituted proteorhodopsin and potassium phosphotungstate nanoparticles. With the observation of an accelerated protein photocycle and elevated proton conductivity, this improvement of the photo-electric performance is attributed to the construction of a 3D proton-transfer framework.
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Affiliation(s)
- Siyuan Rao
- Beijing Key Laboratory of Bio-inspired Energy Materials and Devices, School of Chemistry and Environment, Beihang University, Beijing, 100191, PR China
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22
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Gruenbaum SM, Skinner JL. Vibrational spectroscopy of water in hydrated lipid multi-bilayers. III. Water clustering and vibrational energy transfer. J Chem Phys 2014; 139:175103. [PMID: 24206336 DOI: 10.1063/1.4827018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Water clustering and connectivity around lipid bilayers strongly influences the properties of membranes and is important for functions such as proton and ion transport. Vibrational anisotropic pump-probe spectroscopy is a powerful tool for understanding such clustering, as the measured anisotropy depends upon the time-scale and degree of intra- and intermolecular vibrational energy transfer. In this article, we use molecular dynamics simulations and theoretical vibrational spectroscopy to help interpret recent experimental measurements of the anisotropy of water in lipid multi-bilayers as a function of both lipid hydration level and isotopic substitution. Our calculations are in satisfactory agreement with the experiments of Piatkowski, Heij, and Bakker, and from our simulations we can directly probe water clustering and connectivity. We find that at low hydration levels, many water molecules are in fact isolated, although up to 70% of hydration water forms small water clusters or chains. At intermediate hydration levels, water forms a wide range of cluster sizes, while at higher hydration levels, the majority of water molecules are part of a large, percolating water cluster. Therefore, the size, number, and nature of water clusters are strongly dependent on lipid hydration level, and the measured anisotropy reflects this through its dependence on intermolecular energy transfer.
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Affiliation(s)
- S M Gruenbaum
- Theoretical Chemistry Institute and Department of Chemistry, 1101 University Ave., University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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23
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Wickstrand C, Dods R, Royant A, Neutze R. Bacteriorhodopsin: Would the real structural intermediates please stand up? Biochim Biophys Acta Gen Subj 2014; 1850:536-53. [PMID: 24918316 DOI: 10.1016/j.bbagen.2014.05.021] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 05/23/2014] [Accepted: 05/29/2014] [Indexed: 11/18/2022]
Abstract
BACKGROUND Bacteriorhodopsin (bR) is the simplest known light driven proton pump and has been heavily studied using structural methods: eighty four X-ray diffraction, six electron diffraction and three NMR structures of bR are deposited within the protein data bank. Twenty one X-ray structures report light induced structural changes and changes induced by mutation, changes in pH, thermal annealing or X-ray induced photo-reduction have also been examined. SCOPE OF REVIEW We argue that light-induced structural changes that are replicated across several studies by independent research groups are those most likely to represent what is happening in reality. We present both internal distance matrix analyses that sort deposited bR structures into hierarchal trees, and difference Fourier analysis of deposited X-ray diffraction data. MAJOR CONCLUSIONS An internal distance matrix analysis separates most wild-type bR structures according to their different crystal forms, indicating how the protein's structure is influenced by crystallization conditions. A similar analysis clusters eleven studies of illuminated bR crystals as one branch of a hierarchal tree with reproducible movements of the extracellular portion of helix C towards helix G, and of the cytoplasmic portion of helix F away from helices A, B and G. All crystallographic data deposited for illuminated crystals show negative difference density on a water molecule (Wat402) that forms H-bonds to the retinal Schiff Base and two aspartate residues (Asp85, Asp212) in the bR resting state. Other recurring difference density features indicated reproducible side-chain, backbone and water molecule displacements. X-ray induced radiation damage also disorders Wat402 but acts via cleaving the head-groups of Asp85 and Asp212. GENERAL SIGNIFICANCE A remarkable level of agreement exists when deposited structures and crystallographic observations are viewed as a whole. From this agreement a unified picture of the structural mechanism of light-induced proton pumping by bR emerges. This article is part of a Special Issue entitled Structural biochemistry and biophysics of membrane proteins.
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Affiliation(s)
- Cecilia Wickstrand
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530 Gothenburg, Sweden
| | - Robert Dods
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530 Gothenburg, Sweden
| | - Antoine Royant
- Univ. Grenoble Alpes, IBS, F-38044 Grenoble, France; CNRS, IBS, F-38044 Grenoble, France; CEA, IBS, F-38044 Grenoble, France; European Synchrotron Radiation Facility, F-38043 Grenoble, France.
| | - Richard Neutze
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530 Gothenburg, Sweden.
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24
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Effects of Triton X-100 on Proton Transfer and in the Photocycle of Archaerhodopsin 4. Biosci Biotechnol Biochem 2014; 76:250-6. [DOI: 10.1271/bbb.110508] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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25
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Effects of Mutations of Lys41 and Asp102 of Bacteriorhodopsin. Biosci Biotechnol Biochem 2014; 75:1364-70. [DOI: 10.1271/bbb.110180] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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26
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Pastorczak M, van der Post ST, Bakker HJ. Cooperative hydration of carboxylate groups with alkali cations. Phys Chem Chem Phys 2014; 15:17767-70. [PMID: 24068108 DOI: 10.1039/c3cp52419a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We study the orientational dynamics of water molecules in solutions of formate salts using femtosecond mid-infrared spectroscopy. We observe that combining the formate ion with small cations like Na(+) or Li(+) leads to a cooperative effect on the water dynamics. This observation points at the formation of solvent-separated ion pairs.
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Affiliation(s)
- Marcin Pastorczak
- FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands.
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27
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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
![]()
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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28
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Linke K, Ho FM. Water in Photosystem II: Structural, functional and mechanistic considerations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:14-32. [DOI: 10.1016/j.bbabio.2013.08.003] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 08/08/2013] [Accepted: 08/13/2013] [Indexed: 12/30/2022]
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29
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Monitoring protein-ligand interactions by time-resolved FTIR difference spectroscopy. Methods Mol Biol 2013; 1008:299-323. [PMID: 23729257 DOI: 10.1007/978-1-62703-398-5_11] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2023]
Abstract
Time-resolved FTIR difference spectroscopy is a valuable tool to monitor the dynamics and exact molecular details of protein-ligand interactions. FTIR difference spectroscopy selects, out of the background absorbance of the whole sample, the absorbance bands of the protein groups and of the ligands that are involved in the protein reaction. The absorbance changes can be monitored with time-resolutions down to nanoseconds and followed for time periods ranging over nine orders of magnitude even in membrane proteins with a size of 100,000 Da. Here, we discuss the various experimental setups. The rapid scan technique allows a time resolution in the millisecond regime, whereas the step scan technique allows nanosecond time resolution. We show appropriate sample cells and how to trigger a reaction within these cells. The kinetic analysis of the data is discussed. A crucial step in the data analysis is the reliable assignment of bands to chemical groups of the protein and the ligand. This is done either by site directed mutagenesis, where the absorbance bands of the exchanged amino acids disappear or by isotopically labeling, where the band of the labelled group is frequency shifted.
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30
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Lórenz-Fonfría VA, Heberle J. Channelrhodopsin unchained: structure and mechanism of a light-gated cation channel. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:626-42. [PMID: 24212055 DOI: 10.1016/j.bbabio.2013.10.014] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 10/21/2013] [Accepted: 10/30/2013] [Indexed: 12/25/2022]
Abstract
The new and vibrant field of optogenetics was founded by the seminal discovery of channelrhodopsin, the first light-gated cation channel. Despite the numerous applications that have revolutionised neurophysiology, the functional mechanism is far from understood on the molecular level. An arsenal of biophysical techniques has been established in the last decades of research on microbial rhodopsins. However, application of these techniques is hampered by the duration and the complexity of the photoreaction of channelrhodopsin compared with other microbial rhodopsins. A particular interest in resolving the molecular mechanism lies in the structural changes that lead to channel opening and closure. Here, we review the current structural and mechanistic knowledge that has been accomplished by integrating the static structure provided by X-ray crystallography and electron microscopy with time-resolved spectroscopic and electrophysiological techniques. The dynamical reactions of the chromophore are effectively coupled to structural changes of the protein, as shown by ultrafast spectroscopy. The hierarchical sequence of structural changes in the protein backbone that spans the time range from 10(-12)s to 10(-3)s prepares the channel to open and, consequently, cations can pass. Proton transfer reactions that are associated with channel gating have been resolved. In particular, glutamate 253 and aspartic acid 156 were identified as proton acceptor and donor to the retinal Schiff base. The reprotonation of the latter is the critical determinant for channel closure. The proton pathway that eventually leads to proton pumping is also discussed. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks.
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Affiliation(s)
- Víctor A Lórenz-Fonfría
- Freie Universität Berlin, Experimental Molecular Biophysics, Arnimallee 14, 14195 Berlin, Germany
| | - Joachim Heberle
- Freie Universität Berlin, Experimental Molecular Biophysics, Arnimallee 14, 14195 Berlin, Germany.
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31
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Bao H, Dilbeck PL, Burnap RL. Proton transport facilitating water-oxidation: the role of second sphere ligands surrounding the catalytic metal cluster. PHOTOSYNTHESIS RESEARCH 2013; 116:215-229. [PMID: 23975203 DOI: 10.1007/s11120-013-9907-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 08/03/2013] [Indexed: 06/02/2023]
Abstract
The ability of PSII to extract electrons from water, with molecular oxygen as a by-product, is a remarkable biochemical and evolutionary innovation. From an evolutionary perspective, the invention of PSII approximately 2.7 Ga led to the accelerated accumulation of biomass in the biosphere and the accumulation of oxygen in the atmosphere, a combination that allowed for the evolution of a much more complex and extensive biosphere than would otherwise have been possible. From the biochemical and enzymatic perspective, PSII is remarkable because of the thermodynamic and kinetic obstacles that needed to have been overcome to oxidize water as the ultimate photosynthetic electron donor. This article focuses on how proton release is an integral part of how these kinetic and thermodynamic obstacles have been overcome: the sequential removal of protons from the active site of H2O-oxidation facilitates the multistep oxidation of the substrate water at the Mn4CaOx, the catalytic heart of the H2O-oxidation reaction. As noted previously, the facilitated deprotonation of the Mn4CaOx cluster exerts a redox-leveling function preventing the accumulation of excess positive charge on the cluster, which might otherwise hinder the already energetically difficult oxidation of water. Using recent results, including the characteristics of site-directed mutants, the role of the second sphere of amino acid ligands and the associated network of water molecules surrounding the Mn4CaOx is discussed in relation to proton transport in other systems. In addition to the redox-leveling function, a trapping function is assigned to the proton release step occurring immediately prior to the dioxygen chemistry. This trapping appears to involve a yet-to-be clarified gating mechanism that facilitates to coordinated release of a proton from the neighborhood of the active site thereby insuring that the backward charge-recombination reaction does not out-compete the forward reaction of dioxygen chemistry during this final step of H2O-oxidation.
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Affiliation(s)
- Han Bao
- Department of Microbiology and Molecular Genetics, Oklahoma State University, 307 Life Sciences East, Stillwater, OK, 74078, USA
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Gerwert K, Freier E, Wolf S. The role of protein-bound water molecules in microbial rhodopsins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:606-13. [PMID: 24055285 DOI: 10.1016/j.bbabio.2013.09.006] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Revised: 09/08/2013] [Accepted: 09/10/2013] [Indexed: 02/06/2023]
Abstract
Protein-bound internal water molecules are essential features of the structure and function of microbial rhodopsins. Besides structural stabilization, they act as proton conductors and even proton storage sites. Currently, the most understood model system exhibiting such features is bacteriorhodopsin (bR). During the last 20 years, the importance of water molecules for proton transport has been revealed through this protein. It has been shown that water molecules are as essential as amino acids for proton transport and biological function. In this review, we present an overview of the historical development of this research on bR. We furthermore summarize the recently discovered protein-bound water features associated with proton transport. Specifically, we discuss a pentameric water/amino acid arrangement close to the protonated Schiff base as central proton-binding site, a protonated water cluster as proton storage site at the proton-release site, and a transient linear water chain at the proton uptake site. We highlight how protein conformational changes reposition or reorient internal water molecules, thereby guiding proton transport. Last, we compare the water positions in bR with those in other microbial rhodopsins to elucidate how protein-bound water molecules guide the function of microbial rhodopsins. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks.
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Affiliation(s)
- Klaus Gerwert
- Department of Biophysics, University of Bochum, ND 04 North, 44780 Bochum, Germany; Department of Biophysics, Chinese Academy of Sciences-Max-Planck Partner Institute for Computational Biology (PICB), Shanghai Institutes for Biological Sciences (SIBS), 320 Yue Yang Lu, 200031 Shanghai, PR China.
| | - Erik Freier
- Department of Biophysics, University of Bochum, ND 04 North, 44780 Bochum, Germany
| | - Steffen Wolf
- Department of Biophysics, Chinese Academy of Sciences-Max-Planck Partner Institute for Computational Biology (PICB), Shanghai Institutes for Biological Sciences (SIBS), 320 Yue Yang Lu, 200031 Shanghai, PR China
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Wang T, Sessions AO, Lunde CS, Rouhani S, Glaeser RM, Duan Y, Facciotti MT. Deprotonation of D96 in bacteriorhodopsin opens the proton uptake pathway. Structure 2013; 21:290-7. [PMID: 23394942 DOI: 10.1016/j.str.2012.12.018] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2012] [Revised: 12/08/2012] [Accepted: 12/12/2012] [Indexed: 11/18/2022]
Abstract
Despite extensive investigation, the precise mechanism controlling the opening of the cytoplasmic proton uptake pathway in bacteriorhodopsin (bR) has remained a mystery. From an analysis of the X-ray structure of the D96G/F171C/F219L triple mutant of bR and 60 independent molecular dynamics simulations of bR photointermediates, we report that the deprotonation of D96, a key residue in proton transfer reactions, serves two roles that occur sequentially. First, D96 donates a proton to the Schiff base. Subsequently, the deprotonation of D96 serves to "unlatch" the cytoplasmic side. The latching function of D96 appears to be remarkably robust, functioning to open hydration channels in all photointermediate structures. These results suggest that the protonation state of D96 may be the critical biophysical cue controlling the opening and closing of the cytoplasmic half-channel in bR. We suspect that this protonation-switch mechanism could also be utilized in other proton pumps to minimize backflow and reinforce directionality.
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Affiliation(s)
- Ting Wang
- Genome Center and Department of Biomedical Engineering, University of California at Davis, One Shields Avenue, Davis, CA 95616, USA
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Zhang J, Mizuno K, Murata Y, Koide H, Murakami M, Ihara K, Kouyama T. Crystal structure of deltarhodopsin-3 from Haloterrigena thermotolerans. Proteins 2013; 81:1585-92. [DOI: 10.1002/prot.24316] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Revised: 03/25/2013] [Accepted: 04/03/2013] [Indexed: 11/06/2022]
Affiliation(s)
- Jin Zhang
- Department of Physics; Graduate School of Science; Nagoya University; Nagoya Japan
| | - Katsuhide Mizuno
- Department of Physics; Graduate School of Science; Nagoya University; Nagoya Japan
| | - Yuki Murata
- Department of Physics; Graduate School of Science; Nagoya University; Nagoya Japan
| | - Hideaki Koide
- Department of Physics; Graduate School of Science; Nagoya University; Nagoya Japan
| | - Midori Murakami
- Department of Physics; Graduate School of Science; Nagoya University; Nagoya Japan
| | - Kunio Ihara
- Center for Gene Research; Nagoya University; Nagoya Japan
| | - Tsutomu Kouyama
- Department of Physics; Graduate School of Science; Nagoya University; Nagoya Japan
- RIKEN Harima Institute/SPring-8, 1-1-1; Kouto Mikazuki, Sayo, Hyogo Japan
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Morgan JE, Vakkasoglu AS, Lanyi JK, Lugtenburg J, Gennis RB, Maeda A. Structure changes upon deprotonation of the proton release group in the bacteriorhodopsin photocycle. Biophys J 2013; 103:444-452. [PMID: 22947860 DOI: 10.1016/j.bpj.2012.06.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Revised: 05/19/2012] [Accepted: 06/04/2012] [Indexed: 11/18/2022] Open
Abstract
In the photocycle of bacteriorhodopsin at pH 7, a proton is ejected to the extracellular medium during the protonation of Asp-85 upon formation of the M intermediate. The group that releases the ejected proton does not become reprotonated until the prephotolysis state is restored from the N and O intermediates. In contrast, at acidic pH, this proton release group remains protonated to the end of the cycle. Time-resolved Fourier transform infrared measurements obtained at pH 5 and 7 were fitted to obtain spectra of kinetic intermediates, from which the spectra of M and N/O versus unphotolyzed state were calculated. Vibrational features that appear in both M and N/O spectra at pH 7, but not at pH 5, are attributable to deprotonation from the proton release group and resulting structural alterations. Our results agree with the earlier conclusion that this group is a protonated internal water cluster, and provide a stronger experimental basis for this assignment. A decrease in local polarity at the N-C bond of the side chain of Lys-216 resulting from deprotonation of this water cluster may be responsible for the increase in the proton affinity of Asp-85 through M and N/O, which is crucial for maintaining the directionality of proton pumping.
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Affiliation(s)
- Joel E Morgan
- Department of Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York
| | - Ahmet S Vakkasoglu
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Janos K Lanyi
- Department of Physiology and Biophysics, University of California, Irvine, California
| | - Johan Lugtenburg
- Department of Chemistry, University of Leiden, Leiden, The Netherlands
| | - Robert B Gennis
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois; Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Akio Maeda
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois.
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Abrusci P, Vergara–Irigaray M, Johnson S, Beeby MD, Hendrixson D, Roversi P, Friede ME, Deane JE, Jensen GJ, Tang CM, Lea SM. Architecture of the major component of the type III secretion system export apparatus. Nat Struct Mol Biol 2013; 20:99-104. [PMID: 23222644 PMCID: PMC3537844 DOI: 10.1038/nsmb.2452] [Citation(s) in RCA: 167] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 10/22/2012] [Indexed: 12/20/2022]
Abstract
Type III secretion systems (T3SSs) are bacterial membrane-embedded nanomachines designed to export specifically targeted proteins from the bacterial cytoplasm. Secretion through T3SS is governed by a subset of inner membrane proteins termed the 'export apparatus'. We show that a key member of the Shigella flexneri export apparatus, MxiA, assembles into a ring essential for secretion in vivo. The ring-forming interfaces are well-conserved in both nonflagellar and flagellar homologs, implying that the ring is an evolutionarily conserved feature in these systems. Electron cryo-tomography revealed a T3SS-associated cytoplasmic torus of size and shape corresponding to those of the MxiA ring aligned to the secretion channel located between the secretion pore and the ATPase complex. This defines the molecular architecture of the dominant component of the export apparatus and allows us to propose a model for the molecular mechanisms controlling secretion.
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Affiliation(s)
- Patrizia Abrusci
- Sir William Dunn School of Pathology, Oxford University, Oxford, United Kingdom
| | - Marta Vergara–Irigaray
- Sir William Dunn School of Pathology, Oxford University, Oxford, United Kingdom
- Centre for Molecular Microbiology and Infection, Imperial College London, London, United Kingdom
| | - Steven Johnson
- Sir William Dunn School of Pathology, Oxford University, Oxford, United Kingdom
| | - Morgan D Beeby
- Department of Biology, California Institute of Technology, Pasadena, California, USA
- Howard Hughes Medical Institute, California Institute of Technology, Pasadena, California, USA
| | - David Hendrixson
- Department of Microbiology, UT Southwestern Medical Center, Dallas, Texas, USA
| | - Pietro Roversi
- Sir William Dunn School of Pathology, Oxford University, Oxford, United Kingdom
| | - Miriam E Friede
- Sir William Dunn School of Pathology, Oxford University, Oxford, United Kingdom
| | - Janet E Deane
- Sir William Dunn School of Pathology, Oxford University, Oxford, United Kingdom
| | - Grant J Jensen
- Department of Biology, California Institute of Technology, Pasadena, California, USA
- Howard Hughes Medical Institute, California Institute of Technology, Pasadena, California, USA
| | - Christoph M Tang
- Sir William Dunn School of Pathology, Oxford University, Oxford, United Kingdom
| | - Susan M Lea
- Sir William Dunn School of Pathology, Oxford University, Oxford, United Kingdom
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Herzog E, Gu W, Juhnke H, Haas A, Mäntele W, Simon J, Helms V, Lancaster C. Hydrogen-bonded networks along and bifurcation of the E-pathway in quinol:fumarate reductase. Biophys J 2012; 103:1305-14. [PMID: 22995503 PMCID: PMC3446689 DOI: 10.1016/j.bpj.2012.07.037] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 07/24/2012] [Accepted: 07/25/2012] [Indexed: 02/06/2023] Open
Abstract
The E-pathway of transmembrane proton transfer has been demonstrated previously to be essential for catalysis by the diheme-containing quinol:fumarate reductase (QFR) of Wolinella succinogenes. Two constituents of this pathway, Glu-C180 and heme b(D) ring C (b(D)-C-) propionate, have been validated experimentally. Here, we identify further constituents of the E-pathway by analysis of molecular dynamics simulations. The redox state of heme groups has a crucial effect on the connectivity patterns of mobile internal water molecules that can transiently support proton transfer from the b(D)-C-propionate to Glu-C180. The short H-bonding paths formed in the reduced states can lead to high proton conduction rates and thus provide a plausible explanation for the required opening of the E-pathway in reduced QFR. We found evidence that the b(D)-C-propionate group is the previously postulated branching point connecting proton transfer to the E-pathway from the quinol-oxidation site via interactions with the heme b(D) ligand His-C44. An essential functional role of His-C44 is supported experimentally by site-directed mutagenesis resulting in its replacement with Glu. Although the H44E variant enzyme retains both heme groups, it is unable to catalyze quinol oxidation. All results obtained are relevant to the QFR enzymes from the human pathogens Campylobacter jejuni and Helicobacter pylori.
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Affiliation(s)
- Elena Herzog
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
- Department of Structural Biology, Center of Human and Molecular Biology, Institute of Biophysics, Faculty of Medicine, Saarland University, Homburg, Germany
| | - Wei Gu
- Center for Bioinformatics and Center of Human and Molecular Biology, Saarland University, Saarbrücken, Germany
| | - Hanno D. Juhnke
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Alexander H. Haas
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Werner Mäntele
- Institute of Biophysics, J. W. Goethe University, Frankfurt am Main, Germany
| | - Jörg Simon
- Institute of Molecular Biosciences, J. W. Goethe University, Frankfurt am Main, Germany
| | - Volkhard Helms
- Center for Bioinformatics and Center of Human and Molecular Biology, Saarland University, Saarbrücken, Germany
| | - C. Roy D. Lancaster
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
- Department of Structural Biology, Center of Human and Molecular Biology, Institute of Biophysics, Faculty of Medicine, Saarland University, Homburg, Germany
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Molecular dynamics simulations reveal proton transfer pathways in cytochrome C-dependent nitric oxide reductase. PLoS Comput Biol 2012; 8:e1002674. [PMID: 22956904 PMCID: PMC3431322 DOI: 10.1371/journal.pcbi.1002674] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Accepted: 07/22/2012] [Indexed: 01/25/2023] Open
Abstract
Nitric oxide reductases (NORs) are membrane proteins that catalyze the reduction of nitric oxide (NO) to nitrous oxide (N2O), which is a critical step of the nitrate respiration process in denitrifying bacteria. Using the recently determined first crystal structure of the cytochrome c-dependent NOR (cNOR) [Hino T, Matsumoto Y, Nagano S, Sugimoto H, Fukumori Y, et al. (2010) Structural basis of biological N2O generation by bacterial nitric oxide reductase. Science 330: 1666–70.], we performed extensive all-atom molecular dynamics (MD) simulations of cNOR within an explicit membrane/solvent environment to fully characterize water distribution and dynamics as well as hydrogen-bonded networks inside the protein, yielding the atomic details of functionally important proton channels. Simulations reveal two possible proton transfer pathways leading from the periplasm to the active site, while no pathways from the cytoplasmic side were found, consistently with the experimental observations that cNOR is not a proton pump. One of the pathways, which was newly identified in the MD simulation, is blocked in the crystal structure and requires small structural rearrangements to allow for water channel formation. That pathway is equivalent to the functional periplasmic cavity postulated in cbb3 oxidase, which illustrates that the two enzymes share some elements of the proton transfer mechanisms and confirms a close evolutionary relation between NORs and C-type oxidases. Several mechanisms of the critical proton transfer steps near the catalytic center are proposed. Denitrification is an anaerobic process performed by several bacteria as an alternative to aerobic respiration. A key intermediate step is catalyzed by the nitric oxide reductase (NOR) enzyme, which is situated in the cytoplasmic membrane. Proton delivery to the catalytic site inside NOR is an important part of its functioning. In this work we use molecular dynamics simulations to describe water distribution and to identify proton transfer pathways in cNOR. Our results reveal two channels from the periplasmic side of the membrane and none from the cytoplasmic side, indicating that cNOR is not a proton pump. It is our hope that these results will provide a basis for further experimental and computational studies aimed to understand details of the NOR mechanism. Furthermore, this work sheds light on the molecular evolution of respiratory enzymes.
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39
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Deckert-Gaudig T, Böhme R, Freier E, Sebesta A, Merkendorf T, Popp J, Gerwert K, Deckert V. Nanoscale distinction of membrane patches--a TERS study of Halobacterium salinarum. JOURNAL OF BIOPHOTONICS 2012; 5:582-91. [PMID: 22371320 DOI: 10.1002/jbio.201100131] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 01/20/2012] [Accepted: 01/20/2012] [Indexed: 05/25/2023]
Abstract
The structural organization of cellular membranes has an essential influence on their functionality. The membrane surfaces currently are considered to consist of various distinct patches, which play an important role in many processes, however, not all parameters such as size and distribution are fully determined. In this study, purple membrane (PM) patches isolated from Halobacterium salinarum were investigated in a first step using TERS (tip-enhanced Raman spectroscopy). The characteristic Raman modes of the resonantly enhanced component of the purple membrane lattice, the retinal moiety of bacteriorhodopsin, were found to be suitable as PM markers. In a subsequent experiment a single Halobacterium salinarum was investigated with TERS. By means of the PM marker bands it was feasible to identify and localize PM patches on the bacterial surface. The size of these areas was determined to be a few hundred nanometers.
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Affiliation(s)
- Tanja Deckert-Gaudig
- Institute of Photonic Technology-IPHT, Albert-Einstein-Strasse 9, 07745 Jena, Germany
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40
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Muroda K, Nakashima K, Shibata M, Demura M, Kandori H. Protein-bound water as the determinant of asymmetric functional conversion between light-driven proton and chloride pumps. Biochemistry 2012; 51:4677-84. [PMID: 22583333 DOI: 10.1021/bi300485r] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Bacteriorhodopsin (BR) and halorhodopsin (HR) are light-driven outward proton and inward chloride pumps, respectively. They have similar protein architecture, being composed of seven-transmembrane helices that bind an all-trans-retinal. BR can be converted into a chloride pump by a single amino acid replacement at position 85, suggesting that BR and HR share a common transport mechanism, and the ionic specificity is determined by the amino acid at that position. However, HR cannot be converted into a proton pump by the corresponding reverse mutation. Here we mutated 6 and 10 amino acids of HR into BR-like, whereas such multiple HR mutants never pump protons. Light-induced Fourier transform infrared spectroscopy revealed that hydrogen bonds of the retinal Schiff base and water are both strong for BR and both weak for HR. Multiple HR mutants exhibit strong hydrogen bonds of the Schiff base, but the hydrogen bond of water is still weak. We concluded that the cause of nonfunctional conversion of HR is the lack of strongly hydrogen-bonded water, the functional determinant of the proton pump.
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Affiliation(s)
- Kosuke Muroda
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya, Japan
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41
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Eisenhauer K, Kuhne J, Ritter E, Berndt A, Wolf S, Freier E, Bartl F, Hegemann P, Gerwert K. In channelrhodopsin-2 Glu-90 is crucial for ion selectivity and is deprotonated during the photocycle. J Biol Chem 2012; 287:6904-11. [PMID: 22219197 PMCID: PMC3307317 DOI: 10.1074/jbc.m111.327700] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The light-activated microbial ion channel channelrhodopsin-2 (ChR2) is a powerful tool to study cellular processes with high spatiotemporal resolution in the emerging field of optogenetics. To customize the channel properties for optogenetic experiments, a detailed understanding of its molecular reaction mechanism is essential. Here, Glu-90, a key residue involved in the gating and selectivity mechanism of the ion channel is characterized in detail. The deprotonation of Glu-90 during the photocycle is elucidated by time-resolved FTIR spectroscopy, which seems to be part of the opening mechanism of the conductive pore. Furthermore, Glu-90 is crucial to ion selectivity as also revealed by mutation of this residue combined with voltage clamp experiments. By dynamic homology modeling, we further hypothesized that the conductive pore is flanked by Glu-90 and located between helices A, B, C, and G.
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Affiliation(s)
- Kirstin Eisenhauer
- Department of Biophysics, Ruhr-University Bochum, Universitätsstrasse 150, Bochum 44801, Germany
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42
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Klimacek M, Brunsteiner M, Nidetzky B. Dynamic mechanism of proton transfer in mannitol 2-dehydrogenase from Pseudomonas fluorescens: mobile GLU292 controls proton relay through a water channel that connects the active site with bulk solvent. J Biol Chem 2011; 287:6655-67. [PMID: 22194597 PMCID: PMC3307286 DOI: 10.1074/jbc.m111.289223] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The active site of mannitol 2-dehydrogenase from Pseudomonas fluorescens (PfM2DH) is connected with bulk solvent through a narrow protein channel that shows structural resemblance to proton channels utilized by redox-driven proton pumps. A key element of the PfM2DH channel is the "mobile" Glu(292), which was seen crystallographically to adopt distinct positions up and down the channel. It was suggested that the "down → up" conformational change of Glu(292) could play a proton relay function in enzymatic catalysis, through direct proton shuttling by the Glu or because the channel is opened for water molecules forming a chain along which the protons flow. We report evidence from site-directed mutagenesis (Glu(292) → Ala) substantiated by data from molecular dynamics simulations that support a role for Glu(292) as a gate in a water chain (von Grotthuss-type) mechanism of proton translocation. Occupancy of the up and down position of Glu(292) is influenced by the bonding and charge state of the catalytic acid base Lys(295), suggesting that channel opening/closing motions of the Glu are synchronized to the reaction progress. Removal of gatekeeper control in the E292A mutant resulted in a selective, up to 120-fold slowing down of microscopic steps immediately preceding catalytic oxidation of mannitol, consistent with the notion that formation of the productive enzyme-NAD(+)-mannitol complex is promoted by a corresponding position change of Glu(292), which at physiological pH is associated with obligatory deprotonation of Lys(295) to solvent. These results underscore the important role of conformational dynamics in the proton transfer steps of alcohol dehydrogenase catalysis.
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Affiliation(s)
- Mario Klimacek
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, A-8010 Graz, Austria
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43
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Riccardi D, Zhu X, Goyal P, Yang S, Hou G, Cui Q. Toward molecular models of proton pumping: Challenges, methods and relevant applications. Sci China Chem 2011. [DOI: 10.1007/s11426-011-4458-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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44
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Plazzo AP, De Franceschi N, Da Broi F, Zonta F, Sanasi MF, Filippini F, Mongillo M. Bioinformatic and mutational analysis of channelrhodopsin-2 protein cation-conducting pathway. J Biol Chem 2011; 287:4818-25. [PMID: 22139833 DOI: 10.1074/jbc.m111.326207] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Channelrhodopsin-2 (ChR2) is a light-gated cation channel widely used as a biotechnological tool to control membrane depolarization in various cell types and tissues. Although several ChR2 variants with modified properties have been generated, the structural determinants of the protein function are largely unresolved. We used bioinformatic modeling of the ChR2 structure to identify the putative cationic pathway within the channel, which is formed by a system of inner cavities that are uniquely present in this microbial rhodopsin. Site-directed mutagenesis combined with patch clamp analysis in HeLa cells was used to determine key residues involved in ChR2 conductance and selectivity. Among them, Gln-56 is important for ion conductance, whereas Ser-63, Thr-250, and Asn-258 are previously unrecognized residues involved in ion selectivity and photocurrent kinetics. This study widens the current structural information on ChR2 and can assist in the design of new improved variants for specific biological applications.
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Affiliation(s)
- Anna Pia Plazzo
- Department of Biomedical Sciences, University of Padova, viale Colombo 3, 35100 Padova, Italy
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45
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Low temperature FTIR spectroscopy provides new insights in the pH-dependent proton pathway of proteorhodopsin. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1583-90. [DOI: 10.1016/j.bbabio.2011.09.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 08/25/2011] [Accepted: 09/05/2011] [Indexed: 11/15/2022]
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46
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Goyal P, Ghosh N, Phatak P, Clemens M, Gaus M, Elstner M, Cui Q. Proton storage site in bacteriorhodopsin: new insights from quantum mechanics/molecular mechanics simulations of microscopic pK(a) and infrared spectra. J Am Chem Soc 2011; 133:14981-97. [PMID: 21761868 PMCID: PMC3178665 DOI: 10.1021/ja201568s] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Identifying the group that acts as the proton storage/loading site is a challenging but important problem for understanding the mechanism of proton pumping in biomolecular proton pumps, such as bacteriorhodopsin (bR) and cytochrome c oxidase. Recent experimental studies of bR propelled the idea that the proton storage/release group (PRG) in bR is not an amino acid but a water cluster embedded in the protein. We argue that this idea is at odds with our knowledge of protein electrostatics, since invoking the water cluster as the PRG would require the protein to raise the pK(a) of a hydronium by almost 11 pK(a) units, which is difficult considering known cases of pK(a) shifts in proteins. Our recent quantum mechanics/molecular mechanics (QM/MM) simulations suggested an alternative "intermolecular proton bond" model in which the stored proton is shared between two conserved Glu residues (194 and 204). Here we show that this model leads to microscopic pK(a) values consistent with available experimental data and the functional requirement of a PRG. Extensive QM/MM simulations also show that, independent of a number of technical issues, such as the influence of QM region size, starting X-ray structure, and nuclear quantum effects, the "intermolecular proton bond" model is qualitatively consistent with available spectroscopic data. Potential of mean force calculations show explicitly that the stored proton strongly prefers the pair of Glu residues over the water cluster. The results and analyses help highlight the importance of considering protein electrostatics and provide arguments for why the "intermolecular proton bond" model is likely applicable to the PRG in biomolecular proton pumps in general.
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Affiliation(s)
- Puja Goyal
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin, Madison, 1101 University Ave, Madison, WI 53706
| | - Nilanjan Ghosh
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin, Madison, 1101 University Ave, Madison, WI 53706
| | - Prasad Phatak
- Department of Physical and Theoretical Chemistry, TU Braunschweig, Hans-Sommer-Straβe 10, D-38106 Braunschweig, Germany
| | - Maike Clemens
- Department of Physical and Theoretical Chemistry, TU Braunschweig, Hans-Sommer-Straβe 10, D-38106 Braunschweig, Germany
| | - Michael Gaus
- Institute of Physical Chemistry, Karlsruhe Institute of Technology, Kaiserstr. 12, 76131 Karlsruhe, Germany
| | - Marcus Elstner
- Department of Physical and Theoretical Chemistry, TU Braunschweig, Hans-Sommer-Straβe 10, D-38106 Braunschweig, Germany
- Institute of Physical Chemistry, Karlsruhe Institute of Technology, Kaiserstr. 12, 76131 Karlsruhe, Germany
| | - Qiang Cui
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin, Madison, 1101 University Ave, Madison, WI 53706
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Proton transfer via a transient linear water-molecule chain in a membrane protein. Proc Natl Acad Sci U S A 2011; 108:11435-9. [PMID: 21709261 DOI: 10.1073/pnas.1104735108] [Citation(s) in RCA: 156] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
High-resolution protein ground-state structures of proton pumps and channels have revealed internal protein-bound water molecules. Their possible active involvement in protein function has recently come into focus. An illustration of the formation of a protonated protein-bound water cluster that is actively involved in proton transfer was described for the membrane protein bacteriorhodopsin (bR) [Garczarek F, Gerwert K (2006) Nature 439:109-112]. Here we show through a combination of time-resolved FTIR spectroscopy and molecular dynamics simulations that three protein-bound water molecules are rearranged by a protein conformational change that resulted in a transient Grotthuss-type proton-transfer chain extending through a hydrophobic protein region of bR. This transient linear water chain facilitates proton transfer at an intermediate conformation only, thereby directing proton transfer within the protein. The rearrangement of protein-bound water molecules that we describe, from inactive positions in the ground state to an active chain in an intermediate state, appears to be energetically favored relative to transient incorporation of water molecules from the bulk. Our discovery provides insight into proton-transfer mechanisms through hydrophobic core regions of ubiquitous membrane spanning proteins such as G-protein coupled receptors or cytochrome C oxidases.
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48
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Lórenz-Fonfría VA, Kandori H, Padrós E. Probing specific molecular processes and intermediates by time-resolved Fourier transform infrared spectroscopy: application to the bacteriorhodopsin photocycle. J Phys Chem B 2011; 115:7972-85. [PMID: 21615095 DOI: 10.1021/jp201739w] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present a general approach for probing the kinetics of specific molecular processes in proteins by time-resolved Fourier transform infrared (IR) spectroscopy. Using bacteriorhodopsin (bR) as a model we demonstrate that by appropriately monitoring some selected IR bands it is possible obtaining the kinetics of the most important events occurring in the photocycle, namely changes in the chromophore and the protein backbone conformation, and changes in the protonation state of the key residues implicated in the proton transfers. Besides confirming widely accepted views of the bR photocycle, our analysis also sheds light into some disputed issues: the degree of retinal torsion in the L intermediate to respect the ground state; the possibility of a proton transfer from Asp85 to Asp212; the relationship between the protonation/deprotonation of Asp85 and the proton release complex; and the timing of the protein backbone dynamics. By providing a direct way to estimate the kinetics of photocycle intermediates the present approach opens new prospects for a robust quantitative kinetic analysis of the bR photocycle, which could also benefit the study of other proteins involved in photosynthesis, in phototaxis, or in respiratory chains.
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Affiliation(s)
- Víctor A Lórenz-Fonfría
- Unitat de Biofísica, Departament de Bioquímica i de Biologia Molecular, and Centre d'Estudis en Biofísica, Universitat Autònoma de Barcelona, Barcelona 08193, Spain.
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Wang B, Cao Z. Hydration of Carbonyl Groups: The Labile H3O+ Ion as an Intermediate Modulated by the Surrounding Water Molecules. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201008239] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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50
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Wang B, Cao Z. Hydration of Carbonyl Groups: The Labile H3O+ Ion as an Intermediate Modulated by the Surrounding Water Molecules. Angew Chem Int Ed Engl 2011; 50:3266-70. [DOI: 10.1002/anie.201008239] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2010] [Revised: 01/23/2011] [Indexed: 11/10/2022]
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