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Okamoto A, Tokunou Y, Kalathil S, Hashimoto K. Proton Transport in the Outer‐Membrane Flavocytochrome Complex Limits the Rate of Extracellular Electron Transport. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201704241] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Akihiro Okamoto
- Global Research Center for Environment and Energy based on Nanomaterials Science National Institute for Material Science 1-1 Namiki, Tsukuba Ibaraki 305-0044 Japan
| | - Yoshihide Tokunou
- Department of Applied Chemistry The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-8656 Japan
| | - Shafeer Kalathil
- Department of Applied Chemistry The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-8656 Japan
| | - Kazuhito Hashimoto
- Global Research Center for Environment and Energy based on Nanomaterials Science National Institute for Material Science 1-1 Namiki, Tsukuba Ibaraki 305-0044 Japan
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Okamoto A, Tokunou Y, Kalathil S, Hashimoto K. Proton Transport in the Outer-Membrane Flavocytochrome Complex Limits the Rate of Extracellular Electron Transport. Angew Chem Int Ed Engl 2017; 56:9082-9086. [PMID: 28608645 PMCID: PMC5575523 DOI: 10.1002/anie.201704241] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Indexed: 01/17/2023]
Abstract
The microbial transfer of electrons to extracellularly located solid compounds, termed extracellular electron transport (EET), is critical for microbial electrode catalysis. Although the components of the EET pathway in the outer membrane (OM) have been identified, the role of electron/cation coupling in EET kinetics is poorly understood. We studied the dynamics of proton transport associated with EET in an OM flavocytochrome complex in Shewanella oneidensis MR‐1. Using a whole‐cell electrochemical assay, a significant kinetic isotope effect (KIE) was observed following the addition of deuterated water (D2O). The removal of a flavin cofactor or key components of the OM flavocytochrome complex significantly increased the KIE in the presence of D2O to values that were significantly larger than those reported for proton channels and ATP synthase, thus indicating that proton transport by OM flavocytochrome complexes limits the rate of EET.
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Affiliation(s)
- Akihiro Okamoto
- Global Research Center for Environment and Energy based on Nanomaterials Science, National Institute for Material Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
| | - Yoshihide Tokunou
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Shafeer Kalathil
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Kazuhito Hashimoto
- Global Research Center for Environment and Energy based on Nanomaterials Science, National Institute for Material Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
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Pokorna S, Jurkiewicz P, Vazdar M, Cwiklik L, Jungwirth P, Hof M. Does fluoride disrupt hydrogen bond network in cationic lipid bilayer? Time-dependent fluorescence shift of Laurdan and molecular dynamics simulations. J Chem Phys 2014; 141:22D516. [DOI: 10.1063/1.4898798] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Sarka Pokorna
- J. Heyrovský Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic v.v.i., Dolejskova 3, 18223 Prague 8, Czech Republic
| | - Piotr Jurkiewicz
- J. Heyrovský Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic v.v.i., Dolejskova 3, 18223 Prague 8, Czech Republic
| | - Mario Vazdar
- Division of Organic Chemistry and Biochemistry, Rudjer Bošković Institute, P.O.B. 180, HR-10002 Zagreb, Croatia
| | - Lukasz Cwiklik
- J. Heyrovský Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic v.v.i., Dolejskova 3, 18223 Prague 8, Czech Republic
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
- Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic v.v.i., Dolejskova 3, 18223 Prague 8, Czech Republic
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Hirakura Y, Sugiyama T, Takeda M, Ikeda M, Yoshioka T. Deuteration as a tool in investigating the role of protons in cell signaling. Biochim Biophys Acta Gen Subj 2010; 1810:218-25. [PMID: 20970482 DOI: 10.1016/j.bbagen.2010.10.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Revised: 10/08/2010] [Accepted: 10/14/2010] [Indexed: 10/18/2022]
Abstract
BACKGROUND The mechanisms underlying the inhibitory effects of deuterium oxide (D₂O; heavy water) are likely to provide insight into the fundamental significance of hydrogen bonds in biological functions. Previously, to begin elucidating the effect of D₂O on physiological functions in living cells, we studied the effects of D₂O on voltage-sensitive Ca²(+) channels in AtT 20 cells and showed that actin distribution, Ca²(+) currents, and β-endorphin release were affected. However, the molecular mechanisms underlying the inhibitory effects of D₂O in whole animals and living cells remain obscure, especially in the effects of D₂O on the cell signaling. METHODS We investigated the molecular mechanisms underlying the inhibitory effects of D₂O on the IP₃-mediated Ca²(+) signaling pathway using Ca²(+) imaging and micro-calorimetric measurements in mGluR1-expressing CHO cells. RESULTS DHPG-induced Ca²(+) elevations were markedly reduced in D₂O. Moreover, the Ca²(+) elevations were completely suppressed in H₂O after receptor activation with DHPG in D₂O, recovering gradually in H₂O medium. Without prior stimulation in D₂O, however, DHPG-induced Ca²(+) elevations in H₂O were not affected. Micro-calorimetric measurements showed reduced total DHPG-evoked heat generation in D₂O, while initial heat production and absorption associated with receptor activation were found to be larger. The reduction of DHPG-induced Ca²(+) elevation and heat generation in D₂O medium may be due to decreased amount of IP₃ by the reduced hydrolysis of PIP₂. GENERAL SIGNIFICANCE Protein structure changes due to the replacement of hydrogen with deuterium will induce the inhibitory effects of D₂O by reduction of the frequency of -OH bonds.
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Affiliation(s)
- Yutaka Hirakura
- Advanced Research Institute for Bioscience, Waseda University, Nishitokyo-shi, Tokyo 202-0021, Japan
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Elsing C, Gosch I, Hennings JC, Hübner CA, Herrmann T. Mechanisms of hypotonic inhibition of the sodium, proton exchanger type 1 (NHE1) in a biliary epithelial cell line (Mz-Cha-1). Acta Physiol (Oxf) 2007; 190:199-208. [PMID: 17581135 DOI: 10.1111/j.1748-1716.2007.01682.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM To elucidate the cellular events that results in inhibition of Na(+), H(+) exchanger type 1 (NHE1) by hypotonicity. METHODS Intracellular pH (pH(i)) was measured in biliary epithelial cells, with the pH-sensitive fluorochrome 2',7'-bis-(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) using a spectrophotometer. Regulatory volume decrease (RVD) was analysed from confocal images. Changes in NHE1 membrane content were visualized by confocal laser scanning microscopy after transfection of Mz-Cha-1 cells with a NHE1-cMyc fusion protein. RESULTS In Mz-Cha-1 cells hypotonicity (-80 mmol L(-1) NaCl) inhibited endogenous Na(+), H(+) exchange. Tyrosine and serine kinase inhibitors were incapable to prevent inhibition. As several signalling pathways influence Na(+), H(+) exchange, we tested the effect of the Ca(++), Calmodulin, protein kinase C or the cAMP, protein kinase A system on inhibition of Na(+), H(+) exchange by hypotonic challenge, but neither system was involved. In contrast, cytoskeleton did influence the effect of hypotonicity. Inhibition of microtubule polymerization by colchicine prevented inhibition of NHE1, and also restored Na(+), H(+) exchange kinetics. Specific inhibition of Src kinases with PP2, attenuated pH(i) recovery rate from 1.93 +/- 0.16 pH units min(-1) (normotonic environment) to 1.02 +/- 0.50 pH units min(-1) (hypotonic environment). Membrane staining of NHE1-cMyc fusion protein was maintained after hypotonic exposure in colchicine pre-treated cells as was RVD. Microfilament inhibition by cytochalasin preserved NHE1 activity. Inhibition of phosphatidylinositol-3'-kinase was unable to restore Na(+), H(+) exchange activity. CONCLUSION We conclude that regulation of Na(+), H(+) exchange during RVD is mediated by cytoskeletal elements. This receptor independent pathway is regulated by Src.
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Affiliation(s)
- C Elsing
- Department of Gastroenterology, St Elisabeth Hospital, Dorsten, Germany
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Elsing C, Gosch I, Hennings JC, Hübner CA, Herrmann T. Mechanisms of hypotonic inhibition of the sodium, proton exchanger type 1 (NHE1) in a biliary epithelial cell line (Mz-Cha-1). Acta Physiol (Oxf) 2007. [DOI: 10.1111/j.1365-201x.2007.01682.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Unno K, Kishido T, Morioka M, Okada S, Oku N. Increased expression of Hsp70 for resistance to deuterium oxide in a yeast mutant cell line. Biol Pharm Bull 2003; 26:799-802. [PMID: 12808289 DOI: 10.1248/bpb.26.799] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Labeling with stable isotopes, typically deuterium (D), is powerful tool for studying the functional structure of biomolecules by NMR. Biosynthesis of certain deuterated proteins in microorganisms cultured in deuterium oxide (D(2)O) is an attractive strategy. However, the growth of almost all microorganisms is inhibited at high concentrations of D(2)O. We isolated a mutant of yeast that grows well in D(2)O. The expression of Hsp70 was enhanced in the mutant. The increased expression also endowed the yeast with cold-resistance. The mutant might be useful for biosynthesis of D-labeled biomolecules.
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Affiliation(s)
- Keiko Unno
- Department of Medical Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan.
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Hübner C, Stremmel W, Elsing C. Sodium, hydrogen exchange type 1 and bile ductular secretory activity in the guinea pig. Hepatology 2000; 31:562-71. [PMID: 10706543 DOI: 10.1002/hep.510310303] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Biliary epithelial cells (BECs) express different Na(+), H(+) exchange (NHE) isoforms. In this study, the potential role of NHE in ductular bile secretion is assessed. Experiments were performed in guinea pig perfused livers and isolated BECs. Inhibition of NHE was achieved by hypotonic stress and by using the unspecific NHE inhibitor, amiloride, or the specific NHE 1 inhibitor, cariporide (HOE 642). Hypotonic stress inhibited basal bile flow by 46% and prevented secretin stimulation of bile flow by reducing biliary bicarbonate output by 50%. Secretin increased bile flow from 3.7 +/- 0.8 microL/min/g to 4.78 microL/min/g (P <.01); subsequent exposure to hypotonic stress decreased secretin-stimulated bile flow by 35% and biliary bicarbonate secretion by approximately 50%. Inhibition of NHE by amiloride or cariporide resulted in a similar reduction of secretin-stimulated bile flow and bicarbonate secretion. Basal bile flow was unaffected by the NHE inhibitors. In isolated guinea pig BECs, regulatory volume decrease and inhibition of NHE was demonstrated after hypotonic stress under basal and secretin-stimulated conditions. In contrast, hypotonic exposure inhibited Cl(-), HCO(3)(-) exchange activity in isolated BECs only during basal conditions but incompletely after secretin stimulation. Our study shows that hypotonic stress inhibits basal bile flow in the guinea pig by inhibition of Cl(-), HCO(3)(-) exchange. NHE1 is not involved in basal bile formation. Increased choleresis after ductular stimulation by secretin depends on intact NHE1 activity. These data indicate that BEC volume changes have profound effects on biliary secretory function.
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Affiliation(s)
- C Hübner
- Department of Medicine, University of Heidelberg, Heidelberg, Germany
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Kushner DJ, Baker A, Dunstall TG. Pharmacological uses and perspectives of heavy water and deuterated compounds. Can J Physiol Pharmacol 1999. [DOI: 10.1139/y99-005] [Citation(s) in RCA: 183] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Since the discovery of D2O (heavy water) and its use as a moderator in nuclear reactors, its biological effects have been extensively, although seldom deeply, studied. This article reviews these effects on whole animals, animal cells, and microorganisms. Both "solvent isotope effects," those due to the special properties of D2O as a solvent, and "deuterium isotope effects" (DIE), which result when D replaces H in many biological molecules, are considered. The low toxicity of D2O toward mammals is reflected in its widespread use for measuring water spaces in humans and other animals. Higher concentrations (usually >20% of body weight) can be toxic to animals and animal cells. Effects on the nervous system and the liver and on formation of different blood cells have been noted. At the cellular level, D2O may affect mitosis and membrane function. Protozoa are able to withstand up to 70% D2O. Algae and bacteria can adapt to grow in 100% D2O and can serve as sources of a large number of deuterated molecules. D2O increases heat stability of macromolecules but may decrease cellular heat stability, possibly as a result of inhibition of chaperonin formation. High D2O concentrations can reduce salt- and ethanol-induced hypertension in rats and protect mice from gamma irradation. Such concentrations are also used in boron neutron capture therapy to increase neutron penetration to boron compounds bound to malignant cells. D2O is more toxic to malignant than normal animal cells, but at concentrations too high for regular therapeutic use. D2O and deuterated drugs are widely used in studies of metabolism of drugs and toxic substances in humans and other animals. The deuterated forms of drugs often have different actions than the protonated forms. Some deuterated drugs show different transport processes. Most are more resistant to metabolic changes, especially those changes mediated by cytochrome P450 systems. Deuteration may also change the pathway of drug metabolism (metabolic switching). Changed metabolism may lead to increased duration of action and lower toxicity. It may also lead to lower activity, if the drug is normally changed to the active form in vivo. Deuteration can also lower the genotoxicity of the anticancer drug tamoxifen and other compounds. Deuteration increases effectiveness of long-chain fatty acids and fluoro-D-phenylalanine by preventing their breakdown by target microorganisms. A few deuterated antibiotics have been prepared, and their antimicrobial activity was found to be little changed. Their action on resistant bacteria has not been studied, but there is no reason to believe that they would be more effective against such bacteria. Insect resistance to insecticides is very often due to insecticide destruction through the cytochrome P450 system. Deuterated insecticides might well be more effective against resistant insects, but this potentially valuable possibility has not yet been studied.Key words: deuterium, heavy water, D2O, deuterium isotope effects.
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DeCoursey TE, Cherny VV. Deuterium isotope effects on permeation and gating of proton channels in rat alveolar epithelium. J Gen Physiol 1997; 109:415-34. [PMID: 9101402 PMCID: PMC2219434 DOI: 10.1085/jgp.109.4.415] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The voltage-activated H+ selective conductance of rat alveolar epithelial cells was studied using whole-cell and excised-patch voltage-clamp techniques. The effects of substituting deuterium oxide, D2O, for water, H2O, on both the conductance and the pH dependence of gating were explored. D+ was able to permeate proton channels, but with a conductance only about 50% that of H+. The conductance in D2O was reduced more than could be accounted for by bulk solvent isotope effects (i.e., the lower mobility of D+ than H+), suggesting that D+ interacts specifically with the channel during permeation. Evidently the H+ or D+ current is not diffusion limited, and the H+ channel does not behave like a water-filled pore. This result indirectly strengthens the hypothesis that H+ (or D+) and not OH- is the ionic species carrying current. The voltage dependence of H- channel gating characteristically is sensitive to pH0 and pHi and was regulated by pD0 and pDi in an analogous manner. shifting 40 mV/U change in the pD gradient. The time constant of H+ current activation was about three times slower (T(act) was larger) in D2O than in H2O. The size of the isotope effect is consistent with deuterium isotope effects for proton abstraction reactions, suggesting that H+ channel activation requires deprotonation of the channel. In contrast, deactivation (T(tail)) was slowed only by a factor < or = 1.5 in D2O. The results are interpreted within the context of a model for the regulation of H+ channel gating by mutually exclusive protonation at internal and external sites (Cherny, V.V., V.S. Markin, and T.E. DeCoursey. 1995. J. Gen. Physiol. 105:861-896). Most of the kinetic effects of D2O can be explained if the pKa of the external regulatory site is approximately 0.5 pH U higher in D2O.
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Affiliation(s)
- T E DeCoursey
- Department of Molecular Biophysics and Physiology, Rush Presbyterian St. Luke's Medical Center, Chicago, Illinois 60612, USA.
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Medina JF, Vazquez JJ, Prieto J. Decreased anion exchanger 2 immunoreactivity in the liver of patients with primary biliary cirrhosis. Hepatology 1997; 25:12-7. [PMID: 8985258 DOI: 10.1002/hep.510250104] [Citation(s) in RCA: 152] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Chloride-bicarbonate anion exchanger 2 (AE2) is expressed in a variety of tissues, including the liver and salivary glands, where it may participate in the generation of hydroionic fluxes into secretions. We have previously reported decreased hepatic levels of AE2 messenger RNA in patients with primary biliary cirrhosis (PBC), a cholestatic condition frequently associated with pluriglandular exocrine failure. Here we investigated the expression of AE2 protein in the liver of PBC patients. Using a monoclonal antibody against an AE2 peptide, immunohistochemistry was performed on liver biopsy specimens from subjects with normal liver (n = 7), patients with PBC (n = 13), and patients with cirrhosis or cholestasis other than PBC (n = 17 and 11, respectively). Immunostaining was graded from 0 to 7, according to its intensity and distribution. AE2 immunoreactivity was observed in normal livers, as previously reported, and in many pathological liver biopsy specimens, being mainly restricted to canaliculi and the luminal membrane of terminal and interlobular bile ducts. Canalicular and ductular scores were significantly reduced in the PBC group compared with each control group (normal liver and cirrhosis or cholestasis other than PBC), whereas no differences in immunoreactivity scores were observed among control groups. When four patients with primary sclerosing cholangitis (PSC) were analyzed, they also differed from those with PBC. These results suggest that PBC is characterized by diminished expression of AE2 in the liver. Reduced levels of this transporter protein might be involved in the pathogenesis of cholestasis in PBC.
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Affiliation(s)
- J F Medina
- Department of Internal Medicine and Liver Unit, University Clinic and Medical School, University of Navarra, Pamplona, Spain
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