1
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Tsujimura M, Saito K, Ishikita H. Stretching vibrational frequencies and pK a differences in H-bond networks of protein environments. Biophys J 2023; 122:4336-4347. [PMID: 37838831 PMCID: PMC10722396 DOI: 10.1016/j.bpj.2023.10.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 08/22/2023] [Accepted: 10/12/2023] [Indexed: 10/16/2023] Open
Abstract
The experimentally measured stretching vibrational frequencies of O-D [νO-D(donor)] and C=O [νC=O(donor)] H-bond donor groups can provide valuable information about the H-bonds in proteins. Here, using a quantum mechanical/molecular mechanical approach, the relationship between these vibrational frequencies and the difference in pKa values between H-bond donor and acceptor groups [ΔpKa(donor … acceptor)] in bacteriorhodopsin and photoactive yellow protein environments was investigated. The results show that νO-D(donor) is correlated with ΔpKa(donor … acceptor), regardless of the specific protein environment. νC=O(donor) is also correlated with ΔpKa(donor … acceptor), although the correlation is weak because the C=O bond does not have a proton. Importantly, the shifts in νO-D(donor) and νC=O(donor) are not caused by changes in pKa(donor) alone, but rather by changes in ΔpKa(donor … acceptor). Specifically, a decrease in ΔpKa(donor … acceptor) can lead to proton release from the H-bond donor group toward the acceptor group, resulting in shifts in the vibrational frequencies of the protein environment. These findings suggest that changes in the stretching vibrational frequencies, in particular νO-D(donor), can be used to monitor proton transfer in protein environments.
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Affiliation(s)
- Masaki Tsujimura
- Department of Advanced Interdisciplinary Studies, The University of Tokyo, Meguro-ku, Tokyo, Japan.
| | - Keisuke Saito
- Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Research Center for Advanced Science and Technology, The University of Tokyo, Meguro-ku, Tokyo, Japan
| | - Hiroshi Ishikita
- Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Research Center for Advanced Science and Technology, The University of Tokyo, Meguro-ku, Tokyo, Japan.
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2
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Zantza I, Pyrris Y, Raniolo S, Papadaki GF, Lambrinidis G, Limongelli V, Diallinas G, Mikros E. Uracil/H + Symport by FurE Refines Aspects of the Rocking-bundle Mechanism of APC-type Transporters. J Mol Biol 2023; 435:168226. [PMID: 37544358 DOI: 10.1016/j.jmb.2023.168226] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 07/22/2023] [Accepted: 07/31/2023] [Indexed: 08/08/2023]
Abstract
Transporters mediate the uptake of solutes, metabolites and drugs across the cell membrane. The eukaryotic FurE nucleobase/H+ symporter of Aspergillus nidulans has been used as a model protein to address structure-function relationships in the APC transporter superfamily, members of which are characterized by the LeuT-fold and seem to operate by the so-called 'rocking-bundle' mechanism. In this study, we reveal the binding mode, translocation and release pathway of uracil/H+ by FurE using path collective variable, funnel metadynamics and rational mutational analysis. Our study reveals a stepwise, induced-fit, mechanism of ordered sequential transport of proton and uracil, which in turn suggests that FurE, functions as a multi-step gated pore, rather than employing 'rocking' of compact domains, as often proposed for APC transporters. Finally, our work supports that specific residues of the cytoplasmic N-tail are involved in substrate translocation, in line with their essentiality for FurE function.
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Affiliation(s)
- Iliana Zantza
- Department of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15771, Greece.
| | - Yiannis Pyrris
- Department of Biology, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15781, Greece.
| | - Stefano Raniolo
- Faculty of Biomedical Sciences, Euler Institute, Università della Svizzera italiana (USI), Lugano 6900, Switzerland.
| | - Georgia F Papadaki
- Department of Biology, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15781, Greece
| | - George Lambrinidis
- Department of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15771, Greece.
| | - Vittorio Limongelli
- Faculty of Biomedical Sciences, Euler Institute, Università della Svizzera italiana (USI), Lugano 6900, Switzerland; Department of Pharmacy, University of Naples "Federico II", Naples 80131, Italy.
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15781, Greece; Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Heraklion 70013, Greece.
| | - Emmanuel Mikros
- Department of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15771, Greece; Athena Research and Innovation Center in Information Communication & Knowledge Technologies, Marousi 15125, Greece.
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3
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Zhang W, Du M, Xi W, Zhang H, Liu SF, Yan J. Platinum Species on Oxygen Vacancy-Rich Titania for Efficient Basic Electrocatalytic Hydrogen Evolution. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:12715-12724. [PMID: 37646100 DOI: 10.1021/acs.langmuir.3c01450] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
Oxygen vacancy-rich titania is a promising support for enhancing the hydrogen evolution reaction (HER). This work innovatively loaded Pt nanoparticles on oxygen vacancy-rich TiO2 (Pt/Vo-TiO2) in situ by using a photocatalytic device. The synthesis conditions are mild, do not require high temperatures and strong reducing agents, and can avoid the accumulation of platinum species. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectrometry (XAS) verified the synergistic effect of Pt species and oxygen vacancies on the progress of the reaction kinetics, where the Pt particles exposed by the in situ synthesis functioned as reaction sites in the electrocatalytic hydrogen evolution. Based on this, Pt/Vo-TiO2 exhibits excellent electrocatalytic performance with an overpotential of only 56 mV at a current density of 10 mA cm-2 and a Tafel slope of only 73.5 mV dec-1. This work provides a new strategy for designing highly efficient HER catalysts.
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Affiliation(s)
- Weikai Zhang
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education; Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, People's Republic of China
| | - Mingxuan Du
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education; Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, People's Republic of China
| | - Wenshan Xi
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education; Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, People's Republic of China
| | - Huiping Zhang
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education; Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, People's Republic of China
| | - Shengzhong Frank Liu
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education; Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, People's Republic of China
| | - Junqing Yan
- Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education; Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710119, People's Republic of China
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4
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Saito K, Nakao S, Ishikita H. Identification of the protonation and oxidation states of the oxygen-evolving complex in the low-dose X-ray crystal structure of photosystem II. FRONTIERS IN PLANT SCIENCE 2023; 14:1029674. [PMID: 37008466 PMCID: PMC10061019 DOI: 10.3389/fpls.2023.1029674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/27/2022] [Accepted: 02/10/2023] [Indexed: 06/19/2023]
Abstract
In photosystem II (PSII), the O3 and O4 sites of the Mn4CaO5 cluster form hydrogen bonds with D1-His337 and a water molecule (W539), respectively. The low-dose X-ray structure shows that these hydrogen bond distances differ between the two homogeneous monomer units (A and B) [Tanaka et al., J. Am Chem. Soc. 2017, 139, 1718]. We investigated the origin of the differences using a quantum mechanical/molecular mechanical (QM/MM) approach. QM/MM calculations show that the short O4-OW539 hydrogen bond (~2.5 Å) of the B monomer is reproduced when O4 is protonated in the S1 state. The short O3-NεHis337 hydrogen bond of the A monomer is due to the formation of a low-barrier hydrogen bond between O3 and doubly-protonated D1-His337 in the overreduced states (S-1 or S-2). It seems plausible that the oxidation state differs between the two monomer units in the crystal.
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Affiliation(s)
- Keisuke Saito
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
- Department of Applied Chemistry, The University of Tokyo, Tokyo, Japan
| | - Shu Nakao
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Hiroshi Ishikita
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
- Department of Applied Chemistry, The University of Tokyo, Tokyo, Japan
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5
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Joutsuka T, Nanasawa R, Igarashi K, Horie K, Sugishima M, Hagiwara Y, Wada K, Fukuyama K, Yano N, Mori S, Ostermann A, Kusaka K, Unno M. Neutron crystallography and quantum chemical analysis of bilin reductase PcyA mutants reveal substrate and catalytic residue protonation states. J Biol Chem 2022; 299:102763. [PMID: 36463961 PMCID: PMC9800206 DOI: 10.1016/j.jbc.2022.102763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Revised: 11/16/2022] [Accepted: 11/29/2022] [Indexed: 12/04/2022] Open
Abstract
PcyA, a ferredoxin-dependent bilin pigment reductase, catalyzes the site-specific reduction of the two vinyl groups of biliverdin (BV), producing phycocyanobilin. Previous neutron crystallography detected both the neutral BV and its protonated form (BVH+) in the wildtype (WT) PcyA-BV complex, and a nearby catalytic residue Asp105 was found to have two conformations (protonated and deprotonated). Semiempirical calculations have suggested that the protonation states of BV are reflected in the absorption spectrum of the WT PcyA-BV complex. In the previously determined absorption spectra of the PcyA D105N and I86D mutants, complexed with BV, a peak at 730 nm, observed in the WT, disappeared and increased, respectively. Here, we performed neutron crystallography and quantum chemical analysis of the D105N-BV and I86D-BV complexes to determine the protonation states of BV and the surrounding residues and study the correlation between the absorption spectra and protonation states around BV. Neutron structures elucidated that BV in the D105N mutant is in a neutral state, whereas that in the I86D mutant is dominantly in a protonated state. Glu76 and His88 showed different hydrogen bonding with surrounding residues compared with WT PcyA, further explaining why D105N and I86D have much lower activities for phycocyanobilin synthesis than the WT PcyA. Our quantum mechanics/molecular mechanics calculations of the absorption spectra showed that the spectral change in D105N arises from Glu76 deprotonation, consistent with the neutron structure. Collectively, our findings reveal more mechanistic details of bilin pigment biosynthesis.
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Affiliation(s)
- Tatsuya Joutsuka
- Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki, Japan,Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Naka-Tokai, Ibaraki, Japan,For correspondence: Tatsuya Joutsuka; Masaki Unno
| | - Ryota Nanasawa
- Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki, Japan
| | - Keisuke Igarashi
- Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki, Japan
| | - Kazuki Horie
- Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki, Japan
| | - Masakazu Sugishima
- Department of Medical Biochemistry, Kurume University School of Medicine, Kurume, Fukuoka, Japan
| | - Yoshinori Hagiwara
- Department of Biochemistry and Applied Chemistry, National Institute of Technology, Kurume College, Kurume, Fukuoka, Japan
| | - Kei Wada
- Department of Medical Sciences, University of Miyazaki, Miyazaki, Miyazaki, Japan
| | - Keiichi Fukuyama
- Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
| | - Naomine Yano
- Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Naka-Tokai, Ibaraki, Japan
| | - Seiji Mori
- Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki, Japan,Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Naka-Tokai, Ibaraki, Japan
| | - Andreas Ostermann
- Heinz Maier-Leibnitz Zentrum (MLZ), Technical University Munich, Garching, Germany
| | - Katsuhiro Kusaka
- Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Naka-Tokai, Ibaraki, Japan
| | - Masaki Unno
- Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki, Japan,Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Naka-Tokai, Ibaraki, Japan,For correspondence: Tatsuya Joutsuka; Masaki Unno
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6
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Absorption wavelength along chromophore low-barrier hydrogen bonds. iScience 2022; 25:104247. [PMID: 35521532 PMCID: PMC9062252 DOI: 10.1016/j.isci.2022.104247] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 03/18/2022] [Accepted: 04/07/2022] [Indexed: 11/22/2022] Open
Abstract
In low-barrier hydrogen bonds (H-bonds), the pKa values for the H-bond donor and acceptor moieties are nearly equal, whereas the redox potential values depend on the H+ position. Spectroscopic details of low-barrier H-bonds remain unclear. Here, we report the absorption wavelength along low-barrier H-bonds in protein environments, using a quantum mechanical/molecular mechanical approach. Low-barrier H-bonds form between Glu46 and p-coumaric acid (pCA) in the intermediate pRCW state of photoactive yellow protein and between Asp116 and the retinal Schiff base in the intermediate M-state of the sodium-pumping rhodopsin KR2. The H+ displacement of only ∼0.4 Å, which does not easily occur without low-barrier H-bonds, is responsible for the ∼50 nm-shift in the absorption wavelength. This may be a basis of how photoreceptor proteins have evolved to proceed photocycles using abundant protons. The low-barrier H-bond formation is a prerequisite for proton transfer How the absorption wavelength changes as H+ moves is an open question The H+ displacement of ∼0.4 Å leads to the absorption wavelength shift of ∼50 nm The localization of the molecular orbitals plays a key role in the wavelength shift
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7
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Gao KX, Zhou Z, Yao L, Wang S, Zhang Y, Zou Q, Ma LX, Wang HX. Aspartic Acid-Assisted Size-Controllable Synthesis of Nanoscale Spherical Covalent Organic Frameworks with Chiral Interfaces for Inhibiting Amyloid-β Fibrillation. ACS APPLIED BIO MATERIALS 2022; 5:1210-1221. [PMID: 35191674 DOI: 10.1021/acsabm.1c01245] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Covalent organic framework nanospheres (COF NSs) have garnered special attention due to their uniform sphere morphology, adjustable particle size, and mesoporous microenvironment. However, methods to control an optimal particle size scale while achieving solution dispersibility and specific surface properties remain underdeveloped, which precludes many of the biomedical applications. Here, we propose and develop a general strategy to access simultaneous size control and surface functionalization of uniform spherical COF NSs in a single step using aspartic acid (d-/l-Asp) that plays center roles in an acid catalyst, hydrophilicity, size-controllable synthesis, and chiral enantiomer. In this study, for the first time, we have employed a surface chemistry engineering study to create a variety of nanoscale spherical COFs and subsequently measure parameters to evaluate the effectiveness of Asp in the regulation of the particle size. Moreover, the potential utilization of the d/l-enantiomeric Asp-COF NSs in preventing β-amyloid (Aβ) aggregation is investigated by analyzing their interactions with Aβ amyloids using a multitechnique experimental approach. To our knowledge, our strategy is the first synthesis of hydrophilic COF NSs with an optimal length scale and a chiral-selective targeting surface, which are crucial for the inhibition of Aβ fibrillation for Alzheimer's disease prevention.
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Affiliation(s)
- Kai-Xiang Gao
- College of Chemistry and Chemical Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang District, Wuhan 430062, China
| | - Zhe Zhou
- Department of Neurology, The First Hospital of Lanzhou University, No. 1 Donggang West Road, Chengguan District, Lanzhou 730000, China
| | - Linli Yao
- College of Chemistry and Chemical Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang District, Wuhan 430062, China
| | - Suxiao Wang
- College of Chemistry and Chemical Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang District, Wuhan 430062, China
| | - Yuexing Zhang
- College of Chemistry and Chemical Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang District, Wuhan 430062, China
| | - Qichao Zou
- College of Chemistry and Chemical Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang District, Wuhan 430062, China
| | - Li-Xin Ma
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Science, Hubei University, No. 368, Youyi Avenue, Wuchang District, Wuhan 430062, China
| | - Hang-Xing Wang
- College of Chemistry and Chemical Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang District, Wuhan 430062, China
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8
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Kiss DJ, Oláh J, Tóth G, Varga M, Stirling A, Menyhárd DK, Ferenczy GG. The Structure-Derived Mechanism of Box H/ACA Pseudouridine Synthase Offers a Plausible Paradigm for Programmable RNA Editing. ACS Catal 2022. [DOI: 10.1021/acscatal.1c04870] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Dóra Judit Kiss
- Medicinal Chemistry Research Group, Research Centre for Natural Sciences, Magyar tudósok krt. 2, H-1117 Budapest, Hungary
| | - Julianna Oláh
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Műegyetem rakpart 3, H-1111 Budapest, Hungary
| | - Gergely Tóth
- Institute of Chemistry, ELTE Eötvös Loránd University, Pázmány P. stny. 1/a, H-1117 Budapest, Hungary
| | - Máté Varga
- Department of Genetics, ELTE Eötvös Loránd University, Pázmány P. stny. 1/c, H-1117 Budapest, Hungary
| | - András Stirling
- Theoretical Chemistry Research Group, Research Centre for Natural Sciences, Magyar tudósok krt. 2, H-1117 Budapest, Hungary
| | - Dóra K. Menyhárd
- MTA-ELTE Protein Modelling Research Group, Institute of Chemistry, ELTE Eötvös Loránd University, Pázmány P. stny. 1/a, H-1117 Budapest, Hungary
| | - György G. Ferenczy
- Medicinal Chemistry Research Group, Research Centre for Natural Sciences, Magyar tudósok krt. 2, H-1117 Budapest, Hungary
- Department of Biophysics and Radiation Biology, Semmelweis University, Tűzoltó u. 37-47, H-1094 Budapest, Hungary
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9
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Sharma G, Merz KM. Formation of the Metal-Binding Core of the ZRT/IRT-like Protein (ZIP) Family Zinc Transporter. Biochemistry 2021; 60:2727-2738. [PMID: 34455776 DOI: 10.1021/acs.biochem.1c00415] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Zinc homeostasis in mammals is constantly and precisely maintained by sophisticated regulatory proteins. Among them, the Zrt/Irt-like protein (ZIP) regulates the influx of zinc into the cytoplasm. In this work, we have employed all-atom molecular dynamics simulations to investigate the Zn2+ transport mechanism in prokaryotic ZIP obtained from Bordetella bronchiseptica (BbZIP) in a membrane bilayer. Additionally, the structural and dynamical transformations of BbZIP during this process have been analyzed. This study allowed us to develop a hypothesis for the zinc influx mechanism and formation of the metal-binding site. We have created a model for the outward-facing form of BbZIP (experimentally only the inward-facing form has been characterized) that has allowed us, for the first time, to observe the Zn2+ ion entering the channel and binding to the negatively charged M2 site. It is thought that the M2 site is less favored than the M1 site, which then leads to metal ion egress; however, we have not observed the M1 site being occupied in our simulations. Furthermore, removing both Zn2+ ions from this complex resulted in the collapse of the metal-binding site, illustrating the "structural role" of metal ions in maintaining the binding site and holding the proteins together. Finally, due to the long Cd2+-residue bond distances observed in the X-ray structures, we have proposed the existence of an H3O+ ion at the M2 site that plays an important role in protein stability in the absence of the metal ion.
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Affiliation(s)
- Gaurav Sharma
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Kenneth M Merz
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States.,Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, United States
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10
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Kaur D, Khaniya U, Zhang Y, Gunner MR. Protein Motifs for Proton Transfers That Build the Transmembrane Proton Gradient. Front Chem 2021; 9:660954. [PMID: 34211960 PMCID: PMC8239185 DOI: 10.3389/fchem.2021.660954] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 05/31/2021] [Indexed: 11/13/2022] Open
Abstract
Biological membranes are barriers to polar molecules, so membrane embedded proteins control the transfers between cellular compartments. Protein controlled transport moves substrates and activates cellular signaling cascades. In addition, the electrochemical gradient across mitochondrial, bacterial and chloroplast membranes, is a key source of stored cellular energy. This is generated by electron, proton and ion transfers through proteins. The gradient is used to fuel ATP synthesis and to drive active transport. Here the mechanisms by which protons move into the buried active sites of Photosystem II (PSII), bacterial RCs (bRCs) and through the proton pumps, Bacteriorhodopsin (bR), Complex I and Cytochrome c oxidase (CcO), are reviewed. These proteins all use water filled proton transfer paths. The proton pumps, that move protons uphill from low to high concentration compartments, also utilize Proton Loading Sites (PLS), that transiently load and unload protons and gates, which block backflow of protons. PLS and gates should be synchronized so PLS proton affinity is high when the gate opens to the side with few protons and low when the path is open to the high concentration side. Proton transfer paths in the proteins we describe have different design features. Linear paths are seen with a unique entry and exit and a relatively straight path between them. Alternatively, paths can be complex with a tangle of possible routes. Likewise, PLS can be a single residue that changes protonation state or a cluster of residues with multiple charge and tautomer states.
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Affiliation(s)
- Divya Kaur
- Department of Chemistry, The Graduate Center, City University of New York, New York, NY, United States.,Department of Physics, City College of New York, New York, NY, United States
| | - Umesh Khaniya
- Department of Physics, City College of New York, New York, NY, United States.,Department of Physics, The Graduate Center, City University of New York, New York, NY, United States
| | - Yingying Zhang
- Department of Physics, City College of New York, New York, NY, United States.,Department of Physics, The Graduate Center, City University of New York, New York, NY, United States
| | - M R Gunner
- Department of Chemistry, The Graduate Center, City University of New York, New York, NY, United States.,Department of Physics, City College of New York, New York, NY, United States.,Department of Physics, The Graduate Center, City University of New York, New York, NY, United States
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11
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Saito K, Nakagawa M, Ishikita H. pK a of the ligand water molecules in the oxygen-evolving Mn 4CaO 5 cluster in photosystem II. Commun Chem 2020; 3:89. [PMID: 36703312 PMCID: PMC9814768 DOI: 10.1038/s42004-020-00336-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 06/30/2020] [Indexed: 01/29/2023] Open
Abstract
Release of the protons from the substrate water molecules is prerequisite for O2 evolution in photosystem II (PSII). Proton-releasing water molecules with low pKa values at the catalytic moiety can be the substrate water molecules. In some studies, one of the ligand water molecules, W2, is regarded as OH-. However, the PSII crystal structure shows neither proton acceptor nor proton-transfer pathway for W2, which is not consistent with the assumption of W2 = OH-. Here we report the pKa values of the four ligand water molecules, W1 and W2 at Mn4 and W3 and W4 at Ca2+, of the Mn4CaO5 cluster. pKa(W1) ≈ pKa(W2) << pKa(W3) ≈ pKa(W4) in the Mn4CaO5 cluster in water. However, pKa(W1) ≈ pKa(D1-Asp61) << pKa(W2) in the PSII protein environment. These results suggest that in PSII, deprotonation of W2 is energetically disfavored as far as W1 exists.
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Affiliation(s)
- Keisuke Saito
- grid.26999.3d0000 0001 2151 536XDepartment of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654 Japan ,grid.26999.3d0000 0001 2151 536XResearch Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 Japan
| | - Minesato Nakagawa
- grid.26999.3d0000 0001 2151 536XDepartment of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654 Japan
| | - Hiroshi Ishikita
- grid.26999.3d0000 0001 2151 536XDepartment of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654 Japan ,grid.26999.3d0000 0001 2151 536XResearch Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 Japan
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12
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Saito K, Mandal M, Ishikita H. Energetics of Ionized Water Molecules in the H-Bond Network near the Ca2+ and Cl– Binding Sites in Photosystem II. Biochemistry 2020; 59:3216-3224. [DOI: 10.1021/acs.biochem.0c00177] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Keisuke Saito
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Manoj Mandal
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Hiroshi Ishikita
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
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13
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Sugishima M, Wada K, Unno M, Fukuyama K. Bilin-metabolizing enzymes: site-specific reductions catalyzed by two different type of enzymes. Curr Opin Struct Biol 2019; 59:73-80. [PMID: 30954759 DOI: 10.1016/j.sbi.2019.03.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2018] [Revised: 01/09/2019] [Accepted: 03/04/2019] [Indexed: 02/05/2023]
Abstract
In mammals, the green heme metabolite biliverdin is converted to a yellow anti-oxidant by NAD(P)H-dependent biliverdin reductase (BVR), whereas in O2-dependent photosynthetic organisms it is converted to photosynthetic or light-sensing pigments by ferredoxin-dependent bilin reductases (FDBRs). In NADP+-bound and biliverdin-bound BVR-A, two biliverdins are stacked at the binding cleft; one is positioned to accept hydride from NADPH, and the other appears to donate a proton to the first biliverdin through a neighboring arginine residue. During the FDBR-catalyzed reaction, electrons and protons are supplied to bilins from ferredoxin and from FDBRs and waters bound within FDBRs, respectively. Thus, the protonation sites of bilin and catalytic residues are important for the analysis of site-specific reduction. The neutron structure of FDBR sheds light on this issue.
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Affiliation(s)
- Masakazu Sugishima
- Department of Medical Biochemistry, Kurume University School of Medicine, Fukuoka 830-0011, Japan.
| | - Kei Wada
- Department of Medical Sciences, University of Miyazaki, Miyazaki 889-1692, Japan
| | - Masaki Unno
- Graduate School of Science and Engineering, Ibaraki University, Ibaraki 316-8511, Japan
| | - Keiichi Fukuyama
- Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan
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14
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Koruza K, Mahon BP, Blakeley MP, Ostermann A, Schrader TE, McKenna R, Knecht W, Fisher SZ. Using neutron crystallography to elucidate the basis of selective inhibition of carbonic anhydrase by saccharin and a derivative. J Struct Biol 2019; 205:147-154. [DOI: 10.1016/j.jsb.2018.12.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 11/30/2018] [Accepted: 12/21/2018] [Indexed: 11/25/2022]
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15
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Stevens DR, Hammes-Schiffer S. Exploring the Role of the Third Active Site Metal Ion in DNA Polymerase η with QM/MM Free Energy Simulations. J Am Chem Soc 2018; 140:8965-8969. [PMID: 29932331 DOI: 10.1021/jacs.8b05177] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The enzyme human DNA polymerase η (Pol η) is critical for bypassing lesions during DNA replication. In addition to the two Mg2+ ions aligning the active site, experiments suggest that a third Mg2+ ion could play an essential catalytic role. Herein the role of this third metal ion is investigated with quantum mechanical/molecular mechanical (QM/MM) free energy simulations of the phosphoryl transfer reaction and a proposed self-activating proton transfer from the incoming nucleotide to the pyrophosphate leaving group. The simulations with only two metal ions in the active site support a sequential mechanism, with phosphoryl transfer followed by relatively fast proton transfer. The simulations with three metal ions in the active site suggest that the third metal ion may play a catalytic role through electrostatic interactions with the leaving group. These electrostatic interactions stabilize the product, making the phosphoryl transfer reaction more thermodynamically favorable with a lower free energy barrier relative to the activated state corresponding to the deprotonated 3'OH nucleophile, and also inhibit the subsequent proton transfer. The possibility that Mg2+-bound hydroxide acts as the base deprotonating the 3'OH nucleophile is also explored.
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Affiliation(s)
- David R Stevens
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
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16
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Wu X, Brooks BR. Hydronium Ions Accompanying Buried Acidic Residues Lead to High Apparent Dielectric Constants in the Interior of Proteins. J Phys Chem B 2018; 122:6215-6223. [PMID: 29771522 DOI: 10.1021/acs.jpcb.8b04584] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Internal ionizable groups are known to play important roles in protein functions. A mystery that has attracted decades of extensive experimental and theoretical studies is the apparent dielectric constants experienced by buried ionizable groups, which are much higher than values expected for protein interiors. Many interpretations have been proposed, such as water penetration, conformational relaxation, local unfolding, protein intrinsic backbone fluctuations, etc. However, these interpretations conflict with many experimental observations. The virtual mixture of multiple states (VMMS) simulation method developed in our lab provides a direct approach for studying the equilibrium of multiple chemical states and can monitor p Ka values along simulation trajectories. Through VMMS simulations of staphylococcal nuclease (SNase) variants with internal Asp or Glu residues, we discovered that cations were attracted to buried deprotonated acidic groups and the presence of the nearby cations were essential to reproduce experimentally measured p Ka values. This finding, combined with structural analysis and validation simulations, suggests that the proton released from a deprotonation process stays near the deprotonated group inside proteins, possibly in the form of a hydronium ion. The existence of a proton near a buried charge has many implications in our understanding of protein functions.
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Affiliation(s)
- Xiongwu Wu
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute (NHLBI) , National Institutes of Health (NIH) , Bethesda , Maryland 20892 , United States
| | - Bernard R Brooks
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute (NHLBI) , National Institutes of Health (NIH) , Bethesda , Maryland 20892 , United States
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17
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Iijima E, Gleeson MP, Unno M, Mori S. QM/MM Investigation for Protonation States in a Bilin Reductase PcyA-Biliverdin IXα Complex. Chemphyschem 2018; 19:1809-1813. [PMID: 29732737 DOI: 10.1002/cphc.201800031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Indexed: 02/28/2024]
Abstract
Herein we report quantum mechanical/molecular mechanical (QM/MM) studies to investigate the most probable protonation states of active site amino acids and bound substrate based on a recently reported neutron diffraction structure of phycocyanobilin:ferredoxin oxidoreductase (PcyA) by Unno et al. This structure was considered to be bound in its initial state of biliverdin IXα (BV), which has the C-pyrrole ring in the deprotonated state. The protonation state of BV suggested by neutron and spectroscopic studies is a stable, two-electron reduced complex with a bound hydronium ion. Several ambiguities in the neutron structure were observed which prompted a further theoretical analysis of the structure. This structural investigation provides new understanding of the PcyA and BV protonation states not previously reported in the literature. Our calculations suggest that the hydronium ion (H3 O+ ) is energetically unfavorable, preferentially protonating the neighboring His88 residue and that the C-ring of BV is not protonated.
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Affiliation(s)
- Eri Iijima
- Institute of Quantum Beam Science, Graduate School of Science and Engineering, Ibaraki University, Mito 310-8512 and Hitachi 316-8511, Ibaraki, Japan
| | - M Paul Gleeson
- Department of Biomedical Engineering, Faculty of Engineering, King Mongkut's institute of Technology Ladkrabang, Thailand
- Department of Chemistry, Faculty of Science, Kasetsart University, Chatuchak, Bangkok, 10903, Thailand
| | - Masaki Unno
- Institute of Quantum Beam Science, Graduate School of Science and Engineering, Ibaraki University, Mito 310-8512 and Hitachi 316-8511, Ibaraki, Japan
- Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Naka, 319-1106, Japan
| | - Seiji Mori
- Institute of Quantum Beam Science, Graduate School of Science and Engineering, Ibaraki University, Mito 310-8512 and Hitachi 316-8511, Ibaraki, Japan
- Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Naka, 319-1106, Japan
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18
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Kawashima K, Takaoka T, Kimura H, Saito K, Ishikita H. O 2 evolution and recovery of the water-oxidizing enzyme. Nat Commun 2018; 9:1247. [PMID: 29593210 PMCID: PMC5871790 DOI: 10.1038/s41467-018-03545-w] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 02/20/2018] [Indexed: 01/14/2023] Open
Abstract
In photosystem II, light-induced water oxidation occurs at the Mn4CaO5 cluster. Here we demonstrate proton releases, dioxygen formation, and substrate water incorporation in response to Mn4CaO5 oxidation in the protein environment, using a quantum mechanical/molecular mechanical approach and molecular dynamics simulations. In S2, H2O at the W1 site forms a low-barrier H-bond with D1-Asp61. In the S2-to-S3 transition, oxidation of OW1H– to OW1•–, concerted proton transfer from OW1H– to D1-Asp61, and binding of a water molecule Wn-W1 at OW1•– are observed. In S4, Wn-W1 facilitates oxo-oxyl radical coupling between OW1•– and corner μ-oxo O4. Deprotonation via D1-Asp61 leads to formation of OW1=O4. As OW1=O4 moves away from Mn, H2O at W539 is incorporated into the vacant O4 site of the O2-evolved Mn4CaO4 cluster, forming a μ-oxo bridge (Mn3–OW539–Mn4) in an exergonic process. Simultaneously, Wn-W1 is incorporated as W1, recovering the Mn4CaO5 cluster. Water splitting during photosynthesis results in the combination of two oxygen atoms to form O2. Here, based on computational simulations, the authors develop a possible mechanism for this reaction, which is different from the mechanisms previous studies have suggested.
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Affiliation(s)
- Keisuke Kawashima
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan
| | - Tomohiro Takaoka
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan
| | - Hiroki Kimura
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan
| | - Keisuke Saito
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan.,Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8904, Japan
| | - Hiroshi Ishikita
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan. .,Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8904, Japan.
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19
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Ikeda T, Saito K, Hasegawa R, Ishikita H. The Existence of an Isolated Hydronium Ion in the Interior of Proteins. Angew Chem Int Ed Engl 2017; 56:9151-9154. [PMID: 28613440 PMCID: PMC5575531 DOI: 10.1002/anie.201705512] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Indexed: 12/20/2022]
Abstract
Neutron diffraction analysis studies reported an isolated hydronium ion (H3O+) in the interior of d‐xylose isomerase (XI) and phycocyanobilin‐ferredoxin oxidoreductase (PcyA). H3O+ forms hydrogen bonds (H‐bonds) with two histidine side‐chains and a backbone carbonyl group in PcyA, whereas H3O+ forms H‐bonds with three acidic residues in XI. Using a quantum mechanical/molecular mechanical (QM/MM) approach, we analyzed stabilization of H3O+ by the protein environment. QM/MM calculations indicated that H3O+ was unstable in the PcyA crystal structure, releasing a proton to an H‐bond partner His88, producing H2O and protonated His88. On the other hand, H3O+ was stable in the XI crystal structure. H‐bond partners of isolated H3O+ would be practically limited to acidic residues such as aspartic and glutamic acids in the protein environment.
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Affiliation(s)
- Takuya Ikeda
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan
| | - Keisuke Saito
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan.,Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8904, Japan
| | - Ryo Hasegawa
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan
| | - Hiroshi Ishikita
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan.,Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8904, Japan
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