1
|
Mohri M, Moghadam A, Burketova L, Ryšánek P. Genome-wide identification of the opsin protein in Leptosphaeria maculans and comparison with other fungi (pathogens of Brassica napus). Front Microbiol 2023; 14:1193892. [PMID: 37692395 PMCID: PMC10485269 DOI: 10.3389/fmicb.2023.1193892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Accepted: 06/28/2023] [Indexed: 09/12/2023] Open
Abstract
The largest family of transmembrane receptors are G-protein-coupled receptors (GPCRs). These receptors respond to perceived environmental signals and infect their host plants. Family A of the GPCR includes opsin. However, there is little known about the roles of GPCRs in phytopathogenic fungi. We studied opsin in Leptosphaeria maculans, an important pathogen of oilseed rape (Brassica napus) that causes blackleg disease, and compared it with six other fungal pathogens of oilseed rape. A phylogenetic tree analysis of 31 isoforms of the opsin protein showed six major groups and six subgroups. All three opsin isoforms of L. maculans are grouped in the same clade in the phylogenetic tree. Physicochemical analysis revealed that all studied opsin proteins are stable and hydrophobic. Subcellular localization revealed that most isoforms were localized in the endoplasmic reticulum membrane except for several isoforms in Verticillium species, which were localized in the mitochondrial membrane. Most isoforms comprise two conserved domains. One conserved motif was observed across all isoforms, consisting of the BACTERIAL_OPSIN_1 domain, which has been hypothesized to have an identical sensory function. Most studied isoforms showed seven transmembrane helices, except for one isoform of V. longisporum and four isoforms of Fusarium oxysporum. Tertiary structure prediction displayed a conformational change in four isoforms of F. oxysporum that presumed differences in binding to other proteins and sensing signals, thereby resulting in various pathogenicity strategies. Protein-protein interactions and binding site analyses demonstrated a variety of numbers of ligands and pockets across all isoforms, ranging between 0 and 13 ligands and 4 and 10 pockets. According to the phylogenetic analysis in this study and considerable physiochemically and structurally differences of opsin proteins among all studied fungi hypothesized that this protein acts in the pathogenicity, growth, sporulation, and mating of these fungi differently.
Collapse
Affiliation(s)
- Marzieh Mohri
- Department of Plant Protection, Faculty of Agrobiology, Food, and Natural Resources, Czech University of Life Sciences, Prague, Czechia
| | - Ali Moghadam
- Institute of Biotechnology, Shiraz University, Shiraz, Iran
| | - Lenka Burketova
- Institute of Experimental Botany, Czech Academy of Sciences, Prague, Czechia
| | - Pavel Ryšánek
- Department of Plant Protection, Faculty of Agrobiology, Food, and Natural Resources, Czech University of Life Sciences, Prague, Czechia
| |
Collapse
|
2
|
Genome-Wide Identification of G Protein-Coupled Receptors in Ciliated Eukaryotes. Int J Mol Sci 2023; 24:ijms24043869. [PMID: 36835283 PMCID: PMC9960496 DOI: 10.3390/ijms24043869] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 02/07/2023] [Accepted: 02/12/2023] [Indexed: 02/17/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are the largest family of transmembrane receptors and play important roles in many physiological processes. As a representative group of protozoa, ciliates represent the highest stage of eukaryotic cell differentiation and evolution in terms of their reproductive mode, two-state karyotype, and extremely diverse cytogenesis patterns. GPCRs have been poorly reported in ciliates. In this study, we identified 492 GPCRs in 24 ciliates. Using the existing classification system for animals, GPCRs in ciliates can be assigned to four families, including families A, B, E, and F. Most (377 members) belong to family A. The number of GPCRs is extremely different in different ciliates; the Heterotrichea ciliates usually have more GPCRs than other ciliates. Parasitic or symbiotic ciliates usually have only a few GPCRs. Gene/genome duplication events seem to play important roles in the expansion of the GPCR superfamily in ciliates. GPCRs in ciliates displayed seven typical domain organizations. GPCRs in an ortholog group are common and conserved in all ciliates. The gene expression analysis of the members in this conserved ortholog group in the model ciliate, Tetrahymena thermophila, suggested that these GPCRs play important roles in the life cycle of ciliates. In summary, this study provides the first comprehensive genome-wide identification of GPCRs in ciliates, improving our understanding of the evolution and function of GPCR in ciliates.
Collapse
|
3
|
Binks L, Tian C, Fielden SDP, Vitorica-Yrezabal IJ, Leigh DA. Transamidation-Driven Molecular Pumps. J Am Chem Soc 2022; 144:15838-15844. [PMID: 35979923 PMCID: PMC9446885 DOI: 10.1021/jacs.2c06807] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We report a new class of synthetic molecular pumps that use a stepwise information ratchet mechanism to achieve the kinetic gating required to sequester their macrocyclic substrates from bulk solution. Threading occurs as a result of active template reactions between the pump terminus amine and an acyl electrophile, whereby the bond-forming reaction is accelerated through the cavity of a crown ether. Carboxylation of the resulting amide results in displacement of the ring to the collection region of the thread. Conversion of the carbamate to a phenolic ester provides an intermediate rotaxane suitable for further pumping cycles. In this way rings can be ratcheted onto a thread from one or both ends of appropriately designed molecular pumps. Each pumping cycle results in one additional ring being added to the thread per terminus acyl group. The absence of pseudorotaxane states ensures that no dethreading of intermediates occurs during the pump operation. This facilitates the loading of different macrocycles in any chosen sequence, illustrated by the pump-mediated synthesis of a [4]rotaxane containing three different macrocycles as a single sequence isomer. A [5]rotaxane synthesized using a dual-opening transamidation pump was structurally characterized by single-crystal X-ray diffraction, revealing a series of stabilizing CH···O interactions between the crown ethers and the polyethylene glycol catchment region of the thread.
Collapse
Affiliation(s)
- Lorna Binks
- Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Chong Tian
- Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Stephen D P Fielden
- Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | | | - David A Leigh
- Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| |
Collapse
|
4
|
Schoelmerich MC, Müller V. Energy-converting hydrogenases: the link between H 2 metabolism and energy conservation. Cell Mol Life Sci 2019; 77:1461-1481. [PMID: 31630229 DOI: 10.1007/s00018-019-03329-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 09/17/2019] [Accepted: 10/01/2019] [Indexed: 10/25/2022]
Abstract
The reversible interconversion of molecular hydrogen and protons is one of the most ancient microbial metabolic reactions and catalyzed by hydrogenases. A widespread yet largely enigmatic group comprises multisubunit [NiFe] hydrogenases, that directly couple H2 metabolism to the electrochemical ion gradient across the membranes of bacteria and of archaea. These complexes are collectively referred to as energy-converting hydrogenases (Ech), as they reversibly transform redox energy into physicochemical energy. Redox energy is typically provided by a low potential electron donor such as reduced ferredoxin to fuel H2 evolution and the establishment of a transmembrane electrochemical ion gradient ([Formula: see text]). The [Formula: see text] is then utilized by an ATP synthase for energy conservation by generating ATP. This review describes the modular structure/function of Ech complexes, focuses on insights into the energy-converting mechanisms, describes the evolutionary context and delves into the implications of relying on an Ech complex as respiratory enzyme for microbial metabolism.
Collapse
Affiliation(s)
- Marie Charlotte Schoelmerich
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, Max-von-Laue-Str. 9, 60438, Frankfurt, Germany.,Microbiology and Biotechnology, Institute of Plant Sciences and Microbiology, Universität Hamburg, Ohnhorststr. 18, 22609, Hamburg, Germany
| | - Volker Müller
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, Max-von-Laue-Str. 9, 60438, Frankfurt, Germany.
| |
Collapse
|
5
|
Investigation of factors influencing oxygen content in Halobacterium salinarum growth medium for improved bacteriorhodopsin production. INTERNATIONAL JOURNAL OF INDUSTRIAL CHEMISTRY 2019. [DOI: 10.1007/s40090-019-0189-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
|
6
|
Abstract
Microorganisms can move towards favorable growth conditions as a response to environmental stimuli. This process requires a motility structure and a system to direct the movement. For swimming motility, archaea employ a rotating filament, the archaellum. This archaea-specific structure is functionally equivalent, but structurally different, from the bacterial flagellum. To control the directionality of movement, some archaea make use of the chemotaxis system, which is used for the same purpose by bacteria. Over the past decades, chemotaxis has been studied in detail in several model bacteria. In contrast, archaeal chemotaxis is much less explored and largely restricted to analyses in halophilic archaea. In this review, we summarize the available information on archaeal taxis. We conclude that archaeal chemotaxis proteins function similarly as their bacterial counterparts. However, because the motility structures are fundamentally different, an archaea-specific docking mechanism is required, for which initial experimental data have only recently been obtained.
Collapse
|
7
|
Amtul Z, Aziz AA. Microbial Proteins as Novel Industrial Biotechnology Hosts to Treat Epilepsy. Mol Neurobiol 2016; 54:8211-8224. [PMID: 27905012 DOI: 10.1007/s12035-016-0279-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 10/31/2016] [Indexed: 12/16/2022]
Abstract
Epilepsy is characterized by the hyperexcitability of various neuronal circuits that results due to the imbalance between glutamate-mediated excitation of voltage-gated cation channels and γ-amino butyric acid (GABA)-mediated inhibition of anion channels leading to aberrant, sporadic oscillations or fluctuations in neuronal electrical activity. Epilepsy with a risk of mortality and around 65 million sufferers of all ages all over the world is limited therapeutically with high rates of adverse reactions, lack of complete seizure control, and over 30% patients with refractory epilepsy. The only alternative to medicines is to identify and surgically remove the seizure foci in the brain or to abort the seizures just as they begin using an implanted cerebral electrode. However, these alternatives are unable to precisely aim aberrant neuronal circuits while leaving others unaltered. Epilepsy animal models also constitute the identical constraint. Thus, a better target-specific approach is needed to study and treat epilepsy. Unicellular green algae Chlamydomonas reinhardtii expresses a channelrhodopsin-2 (ChR2) sodium ion channel protein that controls the phototaxis movement of algae in response to blue light. Similarly, archaeon Natronomonas pharaonis (NpHR) expresses a monovalent Cl- channel protein halorhodopsin that responds to yellow light. These features of ChR2 and NpHR proteins can be used in optogenetic techniques to manipulate the bi-directional firing pattern of neuronal circuits in an attempt to better understand the pathophysiology of epileptic seizures as well as to discover novel potential drugs to treat epilepsy.
Collapse
Affiliation(s)
- Zareen Amtul
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, 75270, Pakistan.
| | - Amal A Aziz
- Sir Wilfrid Laurier Secondary School, Thames Valley District School Board, N6C 4W7, London, ON, Canada
| |
Collapse
|
8
|
Lenton S, Walsh DL, Rhys NH, Soper AK, Dougan L. Structural evidence for solvent-stabilisation by aspartic acid as a mechanism for halophilic protein stability in high salt concentrations. Phys Chem Chem Phys 2016; 18:18054-62. [PMID: 27327567 DOI: 10.1039/c6cp02684b] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Halophilic organisms have adapted to survive in high salt environments, where mesophilic organisms would perish. One of the biggest challenges faced by halophilic proteins is the ability to maintain both the structure and function at molar concentrations of salt. A distinct adaptation of halophilic proteins, compared to mesophilic homologues, is the abundance of aspartic acid on the protein surface. Mutagenesis and crystallographic studies of halophilic proteins suggest an important role for solvent interactions with the surface aspartic acid residues. This interaction, between the regions of the acidic protein surface and the solvent, is thought to maintain a hydration layer around the protein at molar salt concentrations thereby allowing halophilic proteins to retain their functional state. Here we present neutron diffraction data of the monomeric zwitterionic form of aspartic acid solutions at physiological pH in 0.25 M and 2.5 M concentration of potassium chloride, to mimic mesophilic and halophilic-like environmental conditions. We have used isotopic substitution in combination with empirical potential structure refinement to extract atomic-scale information from the data. Our study provides structural insights that support the hypothesis that carboxyl groups on acidic residues bind water more tightly under high salt conditions, in support of the residue-ion interaction model of halophilic protein stabilisation. Furthermore our data show that in the presence of high salt the self-association between the zwitterionic form of aspartic acid molecules is reduced, suggesting a possible mechanism through which protein aggregation is prevented.
Collapse
Affiliation(s)
- Samuel Lenton
- School of Physics and Astronomy, University of Leeds, Leeds, UK.
| | | | | | | | | |
Collapse
|
9
|
Lyu X, Shen C, Fu Y, Xie J, Jiang D, Li G, Cheng J. The Microbial Opsin Homolog Sop1 is involved in Sclerotinia sclerotiorum Development and Environmental Stress Response. Front Microbiol 2016; 6:1504. [PMID: 26779159 PMCID: PMC4703900 DOI: 10.3389/fmicb.2015.01504] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 12/14/2015] [Indexed: 11/29/2022] Open
Abstract
Microbial opsins play a crucial role in responses to various environmental signals. Here, we report that the microbial opsin homolog gene sop1 from the necrotrophic phytopathogenic fungus Sclerotinia sclerotiorum was dramatically up-regulated during infection and sclerotial development compared with the vegetative growth stage. Further, study showed that sop1 was essential for growth, sclerotial development and full virulence of S. sclerotiorum. Sop1-silenced transformants were more sensitive to high salt stress, fungicides and high osmotic stress. However, they were more tolerant to oxidative stress compared with the wild-type strain, suggesting that sop1 is involved in different stress responses and fungicide resistance, which plays a role in the environmental adaptability of S. sclerotiorum. Furthermore, a Delta blast search showed that microbial opsins are absent from the genomes of animals and most higher plants, indicating that sop1 is a potential drug target for disease control of S. sclerotiorum.
Collapse
Affiliation(s)
- Xueliang Lyu
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural UniversityWuhan, China; The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural UniversityWuhan, China
| | - Cuicui Shen
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural UniversityWuhan, China; The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural UniversityWuhan, China
| | - Yanping Fu
- The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China
| | - Jiatao Xie
- The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China
| | - Daohong Jiang
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural UniversityWuhan, China; The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural UniversityWuhan, China
| | - Guoqing Li
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural UniversityWuhan, China; The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural UniversityWuhan, China
| | - Jiasen Cheng
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural UniversityWuhan, China; The Provincial Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural UniversityWuhan, China
| |
Collapse
|
10
|
Mayer F, Müller V. Adaptations of anaerobic archaea to life under extreme energy limitation. FEMS Microbiol Rev 2014; 38:449-72. [DOI: 10.1111/1574-6976.12043] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 08/30/2013] [Accepted: 09/03/2013] [Indexed: 11/28/2022] Open
|
11
|
Kochendoerfer GG, Mathies RA. Ultrafast Spectroscopy of Rhodopsins - Photochemistry at Its Best! Isr J Chem 2013. [DOI: 10.1002/ijch.199500028] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
12
|
Honig B, Ottolenghi M, Sheves M. Acid-Base Equilibria and the Proton Pump in Bacteriorhodopsin. Isr J Chem 2013. [DOI: 10.1002/ijch.199500041] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
13
|
|
14
|
Abstract
Rhodopsins are photochemically reactive membrane proteins that covalently bind retinal chromophores. Type I rhodopsins are found in both prokaryotes and eukaryotic microbes, whereas type II rhodopsins function as photoactivated G-protein coupled receptors (GPCRs) in animal vision. Both rhodopsin families share the seven transmembrane α-helix GPCR fold and a Schiff base linkage from a conserved lysine to retinal in helix G. Nevertheless, rhodopsins are widely cited as a striking example of evolutionary convergence, largely because the two families lack detectable sequence similarity and differ in many structural and mechanistic details. Convergence entails that the shared rhodopsin fold is so especially suited to photosensitive function that proteins from separate origins were selected for this architecture twice. Here we show, however, that the rhodopsin fold is not required for photosensitive activity. We engineered functional bacteriorhodopsin variants with novel folds, including radical noncircular permutations of the α-helices, circular permutations of an eight-helix construct, and retinal linkages relocated to other helices. These results contradict a key prediction of convergence and thereby provide an experimental attack on one of the most intractable problems in molecular evolution: how to establish structural homology for proteins devoid of discernible sequence similarity.
Collapse
|
15
|
|
16
|
Kreuer KD, Wohlfarth A. Limits of Proton Conductivity. Angew Chem Int Ed Engl 2012; 51:10454-6; author reply 10457-8. [DOI: 10.1002/anie.201203887] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2012] [Indexed: 11/06/2022]
|
17
|
Temperature and pH sensitivity of the O(640) intermediate of the bacteriorhodopsin photocycle. Biophys J 2010; 61:1001-6. [PMID: 19431821 DOI: 10.1016/s0006-3495(92)81907-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The temperature and pH dependencies of the O(640) intermediate of the photocycle of bacteriorhodopsin (bR) were investigated by flash photolysis and T-jump experiments. The maximal concentration of the O(640) intermediate was found to be dependent on the temperature, which is described by a sigmoidal relationship. With increasing pH the midpoint of the sigmoidal curves shifts to higher temperatures. The Van't Hoff equation provides enthalpy and entropy values of the observed states. These results indicate that, in the investigated temperature (0-60 degrees C) and pH (pH 4.0-10.0) range, the sequence of the principal intermediates in the pathway "M-N-O-bR" does not change. The observations of the O(640) intermediate at pH < 8.0 and of the N(550) intermediate at pH > 8.0 are most probably due only to changes of the intrinsic rate constants of the bR photocycle, not to a different mechanism.
Collapse
|
18
|
Zhang YN, Sweetman LL, Awad ES, El-Sayed MA. Nature of the individual Ca binding sites in Ca-regenerated bacteriorhodopsin. Biophys J 2010; 61:1201-6. [PMID: 19431830 DOI: 10.1016/s0006-3495(92)81929-x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The binding constants, K(1) and K(2), and the number of Ca(2+) ions in each of the two high affinity sites of Ca(2+)-regenerated bacteriorhodopsin (bR) are determined potentiometrically at different pH values in the range of pH 3.5-4.5 by using the Scatchard plot method. From the pH dependence of K(1) and K(2), it was found that two hydrogen ions are released for each Ca(2+) bound to each of the two high affinity sites. Furthermore, we have measured by a direct spectroscopic method the association constant, K(s), for the binding of Ca(2+) to deionized bR, which is responsible for producing the blue to purple color change. Comparing the value of K(s) and its pH dependence with those of K(1) and K(2) showed that the site corresponding to K(s) is to be identified with that of K(2). This is in agreement with the conclusion reached previously, using a different approach, which showed that it is the second Ca(2+) that causes the blue to purple color change.Our studies also show that in addition to the two distinct high affinity sites, there are about four to six sites with lower binding constants. These are attributed to the nonspecific binding in bR.
Collapse
Affiliation(s)
- Y N Zhang
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024 USA
| | | | | | | |
Collapse
|
19
|
Butt HJ. Measuring local surface charge densities in electrolyte solutions with a scanning force microscope. Biophys J 2010; 63:578-82. [PMID: 19431843 DOI: 10.1016/s0006-3495(92)81601-6] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
To show that local surface charge densities can be measured with a scanning force microscope purple membranes adsorbed to alumina were imaged in electrolyte solutions. Force versus distance curves were measured on purple membranes and on the bare alumina with standard silicon nitride tips. By comparing the electrostatic force measured on both substances, the surface charge density of purple membranes could be calculated from the known charge density of alumina. The charge density of purple membranes was estimated to be -0.05 C/m(2).
Collapse
Affiliation(s)
- H J Butt
- Max-Planck-Institut für Biophysik, Kennedyallee 70, 6000 Frankfurt a. M. 70, Germany
| |
Collapse
|
20
|
Braun-Sand S, Sharma PK, Chu ZT, Pisliakov AV, Warshel A. The energetics of the primary proton transfer in bacteriorhodopsin revisited: it is a sequential light-induced charge separation after all. BIOCHIMICA ET BIOPHYSICA ACTA 2008; 1777:441-52. [PMID: 18387356 PMCID: PMC2443747 DOI: 10.1016/j.bbabio.2008.03.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2007] [Revised: 02/29/2008] [Accepted: 03/03/2008] [Indexed: 11/26/2022]
Abstract
The light-induced proton transport in bacteriorhodopsin has been considered as a model for other light-induced proton pumps. However, the exact nature of this process is still unclear. For example, it is not entirely clear what the driving force of the initial proton transfer is and, in particular, whether it reflects electrostatic forces or other effects. The present work simulates the primary proton transfer (PT) by a specialized combination of the EVB and the QCFF/PI methods. This combination allows us to obtain sufficient sampling and a quantitative free energy profile for the PT at different protein configurations. The calculated profiles provide new insight about energetics of the primary PT and its coupling to the protein conformational changes. Our finding confirms the tentative analysis of an earlier work (A. Warshel, Conversion of light energy to electrostatic energy in the proton pump of Halobacterium halobium, Photochem. Photobiol. 30 (1979) 285-290) and determines that the overall PT process is driven by the energetics of the charge separation between the Schiff base and its counterion Asp85. Apparently, the light-induced relaxation of the steric energy of the chromophore leads to an increase in the ion-pair distance, and this drives the PT process. Our use of the linear response approximation allows us to estimate the change in the protein conformational energy and provides the first computational description of the coupling between the protein structural changes and the PT process. It is also found that the PT is not driven by twist-modulated changes of the Schiff base's pKa, changes in the hydrogen bond directionality, or other non-electrostatic effects. Overall, based on a consistent use of structural information as the starting point for converging free energy calculations, we conclude that the primary event should be described as a light-induced formation of an unstable ground state, whose relaxation leads to charge separation and to the destabilization of the ion-pair state. This provides the driving force for the subsequent PT steps.
Collapse
Affiliation(s)
- Sonja Braun-Sand
- Department of Chemistry, University of Southern California, 418 SGM Building, 3620 McClintock Avenue, Los Angeles, CA 90089-1062, USA
- Department of Chemistry, University of Colorado at Colorado Springs (UCCS), Colorado Springs, CO 80918
| | - Pankaz K. Sharma
- Department of Chemistry, University of Southern California, 418 SGM Building, 3620 McClintock Avenue, Los Angeles, CA 90089-1062, USA
| | - Zhen T. Chu
- Department of Chemistry, University of Southern California, 418 SGM Building, 3620 McClintock Avenue, Los Angeles, CA 90089-1062, USA
| | - Andrei V. Pisliakov
- Department of Chemistry, University of Southern California, 418 SGM Building, 3620 McClintock Avenue, Los Angeles, CA 90089-1062, USA
| | - Arieh Warshel
- Department of Chemistry, University of Southern California, 418 SGM Building, 3620 McClintock Avenue, Los Angeles, CA 90089-1062, USA
| |
Collapse
|
21
|
Saum SH, Müller V. Regulation of osmoadaptation in the moderate halophile Halobacillus halophilus: chloride, glutamate and switching osmolyte strategies. SALINE SYSTEMS 2008; 4:4. [PMID: 18442383 PMCID: PMC2412884 DOI: 10.1186/1746-1448-4-4] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Accepted: 04/28/2008] [Indexed: 11/10/2022]
Abstract
The moderate halophile Halobacillus halophilus is the paradigm for chloride dependent growth in prokaryotes. Recent experiments shed light on the molecular basis of the chloride dependence that is reviewed here. In the presence of moderate salinities Halobacillus halophilus mainly accumulates glutamine and glutamate to adjust turgor. The transcription of glnA2 (encoding a glutamine synthetase) as well as the glutamine synthetase activity were identified as chloride dependent steps. Halobacillus halophilus switches its osmolyte strategy and produces proline as the main compatible solute at high salinities. Furthermore, Halobacillus halophilus also shifts its osmolyte strategy at the transition from the exponential to the stationary phase where proline is exchanged by ectoine. Glutamate was found as a "second messenger" essential for proline production. This observation leads to a new model of sensing salinity by sensing the physico-chemical properties of different anions.
Collapse
Affiliation(s)
- Stephan H Saum
- Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Goethe University Frankfurt, Frankfurt am Main, Germany.
| | | |
Collapse
|
22
|
Subpicosecond midinfrared spectroscopy of the Pfr reaction of phytochrome Agp1 from Agrobacterium tumefaciens. Biophys J 2008; 94:3189-97. [PMID: 18192363 DOI: 10.1529/biophysj.107.119297] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Phytochromes are light-sensing pigments found in plants and bacteria. For the first time, the P(fr) photoreaction of a phytochrome has been subject to ultrafast infrared vibrational spectroscopy. Three time constants of 0.3 ps, 1.3 ps, and 4.0 ps were derived from the kinetics of structurally specific marker bands of the biliverdin chromophore of Agp1-BV from Agrobacterium tumefaciens after excitation at 765 nm. VIS-pump-VIS-probe experiments yield time constants of 0.44 ps and 3.3 ps for the underlying electronic-state dynamics. A reaction scheme is proposed including two kinetic steps on the S(1) excited-state surface and the cooling of a vibrationally hot P(fr) ground state. It is concluded that the upper limit of the E-Z isomerization of the C(15) = C(16) methine bridge is given by the intermediate time constant of 1.3 ps. The reaction scheme is reminiscent of that of the corresponding P(r) reaction of Agp1-BV as published earlier.
Collapse
|
23
|
|
24
|
Quasielastic Neutron Scattering in Biology, Part II: Applications. NEUTRON SCATTERING IN BIOLOGY 2006. [DOI: 10.1007/3-540-29111-3_16] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
25
|
Primary events in the bacteriorhodopsin photocycle: Torsional vibrational dephasing in the first excited electronic state. Chem Phys 2005. [DOI: 10.1016/j.chemphys.2004.12.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
26
|
Girard P, Pécréaux J, Lenoir G, Falson P, Rigaud JL, Bassereau P. A new method for the reconstitution of membrane proteins into giant unilamellar vesicles. Biophys J 2005; 87:419-29. [PMID: 15240476 PMCID: PMC1304363 DOI: 10.1529/biophysj.104.040360] [Citation(s) in RCA: 176] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In this work, we have investigated a new and general method for the reconstitution of membrane proteins into giant unilamellar vesicles (GUVs). We have analyzed systematically the reconstitution of two radically different membrane proteins, the sarcoplasmic reticulum Ca(2+)-ATPase and the H(+) pump bacteriorhodopsin. In a first step, our method involved a detergent-mediated reconstitution of solubilized membrane proteins into proteoliposomes of 0.1-0.2 microm in size. In a second step, these preformed proteoliposomes were partially dried under controlled humidity followed, in a third step, by electroswelling of the partially dried film to give GUVs. The physical characteristics of GUVs were analyzed in terms of morphology, size, and lamellarity using phase-contrast and differential interference contrast microscopy. The reconstitution process was further characterized by analyzing protein incorporation and biological activity. Both membrane proteins could be homogeneously incorporated into GUVs at lipid/protein ratios ranging from 5 to 40 (w/w). After reconstitution, both proteins retained their biological activity as demonstrated by H(+) or Ca(2+) pumping driven by bacteriorhodopsin or Ca(2+)-ATPase, respectively. This constitutes an efficient new method of reconstitution, leading to the production of large unilamellar membrane protein-containing vesicles of more than 20 microm in diameter, which should prove useful for functional and structural studies through the use of optical microscopy, optical tweezers, microelectrodes, or atomic force microscopy.
Collapse
Affiliation(s)
- Philippe Girard
- Laboratoire [corrected] Physico Chimie Cioue, Unité Mixte de Recherche 168 Centre National de la Recherche Scientifique/Institut Curie, 75231 Paris Cedex 05, France.
| | | | | | | | | | | |
Collapse
|
27
|
Hubmacher D, Matzanke BF, Anemüller S. Effects of iron limitation on the respiratory chain and the membrane cytochrome pattern of the Euryarchaeon Halobacterium salinarum. Biol Chem 2004; 384:1565-73. [PMID: 14719798 DOI: 10.1515/bc.2003.173] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The effects of iron limitation on the electron transport chain of the extremely halophilic Euryarchaeon Halobacterium salinarum were analyzed. When iron was growth-limiting, the respiratory rates as well as the inhibition pattern of the membranes were significantly different from membranes of iron replete cells. Changes in the availability of iron cause the formation of different respiratory pathways including different entry sites for electrons, different terminal oxidases of the respiratory chain, and drastic changes of the cytochrome composition and of the relative amounts of cytochromes. Under iron-limiting conditions, mainly low-potential cytochromes were measured. EPR spectroscopic studies revealed that the amount of proteins containing iron-sulfur clusters is reduced in membranes under iron-limiting growth conditions. Taken together, our results strongly suggest for the first time an important role of iron supply for the bioenergetics of an Archaeon.
Collapse
Affiliation(s)
- Dirk Hubmacher
- Institut für Biochemie, Universität zu Lübeck, Ratzeburger Allee 160, D-23538 Lübeck, Germany
| | | | | |
Collapse
|
28
|
Terentis AC, Zhou Y, Atkinson GH, Ujj L. Picosecond Time-Resolved Coherent Anti-Stokes Raman Spectroscopy of the Artificial Bacteriorhodopsin Pigment, BR6.11. J Phys Chem A 2003. [DOI: 10.1021/jp030612g] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Andrew C. Terentis
- Department of Chemistry and Optical Sciences Center, University of Arizona, Tucson, Arizona 85721
| | - Yidong Zhou
- Department of Chemistry and Optical Sciences Center, University of Arizona, Tucson, Arizona 85721
| | - George H. Atkinson
- Department of Chemistry and Optical Sciences Center, University of Arizona, Tucson, Arizona 85721
| | - Laszlo Ujj
- Department of Physics, University of West Florida, Pensacola, Florida 32514
| |
Collapse
|
29
|
Martinez LC, Turner GJ. High-throughput screening of bacteriorhodopsin mutants in whole cell pastes. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1564:91-8. [PMID: 12101000 DOI: 10.1016/s0005-2736(02)00406-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A high-throughput screening method has been developed which enables functional analysis of bacteriorhodpsin in whole cell pastes. Reflectance spectra, from as little as 5 ml of Halobacterium salinarum cells, show close correspondence to that obtained from the purified purple membrane (PM), containing bacteriorhodopsin (BR) as the sole protein component. We demonstrate accurate quantification of BR accumulation by ratiometric analysis of BR (A(max) 568) and a membrane-bound cytochrome (A(max) 410). In addition, ground-state light- and dark-adapted (LA and DA, respectively) spectral differences were determined with high accuracy and precision. Using cells expressing the BR mutant D85N, we monitored transitions between intermediate-state homologues of the reprotonation phase of the light-activated proton pumping mechanism. We demonstrate that phenotypes of three mutants (D85N/T170C, D85N/D96N, and D85N/R82Q) previously characterized for their effect on photocycle transitions are reproduced in the whole cell samples. D85N/T170C stabilizes accumulation of the N state while D85N/D96N accumulates no N state. D85N/R82Q was found to have perturbed the pK(a) of M accumulation. These studies illustrate the correspondence between pH-dependent ground-state transitions accessed by D85N and the transitions accessed by the wild-type protein following photoexcitation. We demonstrate that whole cell reflectance spectroscopy can be used to efficiently characterize the large numbers of mutants generated by engineering strategies that exploit saturation mutagenesis.
Collapse
Affiliation(s)
- Lynell C Martinez
- Department of Physiology and Biophysics and the Neurosciences Program, The University of Miami School of Medicine, Miami, FL 33101, USA
| | | |
Collapse
|
30
|
Lakatos M, Groma GI, Ganea C, Lanyi JK, Váró G. Characterization of the azide-dependent bacteriorhodopsin-like photocycle of salinarum halorhodopsin. Biophys J 2002; 82:1687-95. [PMID: 11916830 PMCID: PMC1301968 DOI: 10.1016/s0006-3495(02)75521-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The photocycle of salinarum halorhodopsin was investigated in the presence of azide. The azide binds to the halorhodopsin with 150 mM binding constant in the absence of chloride and with 250 mM binding constant in the presence of 1 M chloride. We demonstrate that the azide-binding site is different from that of chloride, and the influence of chloride on the binding constant is indirect. The analysis of the absorption kinetic signals indicates the existence of two parallel photocycles. One belongs to the 13-cis retinal containing protein and contains a single red shifted intermediate. The other photocycle, of the all-trans retinal containing halorhodopsin, resembles the cycle of bacteriorhodopsin and contains a long-living M intermediate. With time-resolved spectroscopy, the spectra of intermediates were determined. Intermediates L, N, and O were not detected. The multiexponential rise and decay of the M intermediate could be explained by the introduction of the "spectrally silent" intermediates M1, M2, and HR', HR, respectively. The electric signal measurements revealed the existence of a component equivalent with a proton motion toward the extracellular side of the membrane, which appears during the M1 to M2 transition. The differences between the azide-dependent photocycle of salinarum halorhodopsin and pharaonis halorhodopsin are discussed.
Collapse
Affiliation(s)
- Melinda Lakatos
- Institute of Biophysics, Biological Research Center of the Hungarian Academy of Sciences, Szeged, H-6701, Hungary
| | | | | | | | | |
Collapse
|
31
|
|
32
|
Rothe U, Aurich H, Engelhardt H, Oesterhelt D. Oriented incorporation of bacteriorhodopsin into the lipid shell of phospholipid-coated polymer particles. FEBS Lett 2001. [DOI: 10.1016/0014-5793(90)81401-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
33
|
|
34
|
|
35
|
Persike N, Pfeiffer M, Guckenberger R, Radmacher M, Fritz M. Direct observation of different surface structures on high-resolution images of native halorhodopsin. J Mol Biol 2001; 310:773-80. [PMID: 11453686 DOI: 10.1006/jmbi.2001.4782] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Halorhodopsin (HR) was investigated with atomic force microscopic techniques (AFM) in aqueous solution. Two-dimensional (2D) crystals of HR were obtained by purifying an HR membrane fraction with the same buoyant density as the purple membrane (HR-PM) from the overexpressing strain Halobacterium salinarum D2. The membrane patches of HR were immobilized on mica. Images with a resolution up to 14 A were recorded. Crystals showed an orthogonal structure and the orientation of the molecules showed p42(1)2 symmetry; thus, alternate tetramers are inverted in the membrane. The crystal surface was found to display different structures depending on the imaging force used, indicating that some parts of the HR molecule are more rigid but others more compressible. From samples with single tetramers missing in the crystalline patches dimensions of the unit cell could be determined. Helix-connecting loops in single molecules of halorhodopsin were assigned. The images indicate that the large extracellular BC loop covers the whole molecule and is very flexible.
Collapse
Affiliation(s)
- N Persike
- Physik Department der TU-München, Institut für Biophysik, E22, James-Franck-Str., Garching, 85747, Germany
| | | | | | | | | |
Collapse
|
36
|
Katsu T, Nakagawa H, Kanamori T, Kamo N, Tsuchiya T. Ion-selective electrode for transmembrane pH difference measurements. Anal Chem 2001; 73:1849-54. [PMID: 11338601 DOI: 10.1021/ac001090t] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A triethylammonium-sensitive electrode was constructed using sodium tetrakis[3,5-bis(2-methoxyhexafluoro-2-propyl)phenyl]borate as an ion-exchanger and benzyl 2-nitrophenyl ether as a solvent mediator in a poly(vinylchloride) membrane matrix and was used to determine the pH difference across a cell membrane. The method is based on monitoring of the pH gradient-induced uptake of triethylammonium in situ. The triethylammonium electrode exhibited a near-Nernstian response to triethylammonium in the concentration range of 5 x 10(-6)-1 x 10(-2) M with a slope of 58.5 mV per concentration decade in a buffer solution composed of 150 mM NaCl and 10 mM NaH2PO4/Na2HPO4 (pH 7.5). The limit of detection was 1 microM. In experiments using liposomes, the uptake of triethylammonium into liposomes was quantitatively induced according to the pH difference across the liposomal membrane. The transmembrane pH differences in Escherichia coli cells and the light-induced pH differences across the envelope vesicles of Halobacterium halobium were successfully determined by the present method.
Collapse
Affiliation(s)
- T Katsu
- Faculty of Pharmaceutical Sciences, Okayama University, Tsushima, Okayama 700-8530, Japan.
| | | | | | | | | |
Collapse
|
37
|
Kulcsár A, Groma GI, Lanyi JK, Váró G. Characterization of the proton-transporting photocycle of pharaonis halorhodopsin. Biophys J 2000; 79:2705-13. [PMID: 11053142 PMCID: PMC1301150 DOI: 10.1016/s0006-3495(00)76508-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The photocycle of pharaonis halorhodopsin was investigated in the presence of 100 mM NaN(3) and 1 M Na(2)SO(4). Recent observations established that the replacement of the chloride ion with azide transforms the photocycle from a chloride-transporting one into a proton-transporting one. Kinetic analysis proves that the photocycle is very similar to that of bacteriorhodopsin. After K and L, intermediate M appears, which is missing from the chloride-transporting photocycle. In this intermediate the retinal Schiff base deprotonates. The rise of M in halorhodopsin is in the microsecond range, but occurs later than in bacteriorhodopsin, and its decay is more accentuated multiphasic. Intermediate N cannot be detected, but a large amount of O accumulates. The multiphasic character of the last step of the photocycle could be explained by the existence of a HR' state, as in the chloride photocycle. Upon replacement of chloride ion with azide, the fast electric signal changes its sign from positive to negative, and becomes similar to that detected in bacteriorhodopsin. The photocycle is enthalpy-driven, as is the chloride photocycle of halorhodopsin. These observations suggest that, while the basic charge translocation steps become identical to those in bacteriorhodopsin, the storage and utilization of energy during the photocycle remains unchanged by exchanging chloride with azide.
Collapse
Affiliation(s)
- A Kulcsár
- Institute of Biophysics, Biological Research Center of the Hungarian Academy of Sciences, Szeged, H-6701, Hungary
| | | | | | | |
Collapse
|
38
|
Abstract
The light-activated proton-pumping bacteriorhodopsin and chloride ion-pumping halorhodopsin are compared. They belong to the family of retinal proteins, with 25% amino acid sequence homology. Both proteins have seven alpha helices across the membrane, surrounding the retinal binding pocket. Photoexcitation of all-trans retinal leads to ion transporting photocycles, which exhibit great similarities in the two proteins, despite the differences in the ion transported. The spectra of the K, L, N and O intermediates, calculated using time-resolved spectroscopic measurements, are very similar in both proteins. The absorption kinetic measurements reveal that the chloride ion transporting photocycle of halorhodopsin does not have intermediate M characteristic for deprotonated Schiff base, and intermediate L dominates the process. Energetically the photocycle of bacteriorhodopsin is driven mostly by the decrease of the entropic energy, while the photocycle of halorhodopsin is enthalpy-driven. The ion transporting steps were characterized by the electrogenicity of the intermediates, calculated from the photoinduced transient electric signal measurements. The function of both proteins could be described with the 'local access' model developed for bacteriorhodopsin. In the framework of this model it is easy to understand how bacteriorhodopsin can be converted into a chloride pump, and halorhodopsin into a proton pump, by changing the ion specificity with added ions or site-directed mutagenesis.
Collapse
Affiliation(s)
- G Váró
- Institute of Biophysics, Biological Research Center of the Hungarian Academy of Sciences, H-6701, Szeged, Hungary
| |
Collapse
|
39
|
Abstract
Oriented gel samples were prepared from halorhodopsin-containing membranes from Natronobacterium pharaonis, and their photoelectric responses to laser flash excitation were measured at different chloride concentrations. The fast component of the current signal displayed a characteristic dependency on chloride concentration, and could be interpreted as a sum of two signals that correspond to the responses at high-chloride and no-chloride, but high-sulfate, concentration. The chloride concentration-dependent transition between the two signals followed the titration curve determined earlier from spectroscopic titration. The voltage signal was very similar to that reported by another group (Kalaidzidis, I. V., Y. L. Kalaidzidis, and A. D. Kaulen. 1998. FEBS Lett. 427:59-63). The absorption kinetics, measured at four wavelengths, fit the kinetic model we had proposed earlier. The calculated time-dependent concentrations of the intermediates were used to fit the voltage signal. Although no negative electric signal was observed at high chloride concentration, the calculated electrogenicity of the K intermediate was negative, and very similar to that of bacteriorhodopsin. The late photocycle intermediates (O, HR', and HR) had almost equal electrogenicities, explaining why no chloride-dependent time constant was identified earlier by Kalaidzidis et al. The calculated electrogenicities, and the spectroscopic information for the chloride release and uptake steps of the photocycle, suggest a mechanism for the chloride-translocation process in this pump.
Collapse
Affiliation(s)
- K Ludmann
- Institute of Biophysics, Biological Research Center of the Hungarian Academy of Sciences, Szeged H-6701, Hungary
| | | | | | | |
Collapse
|
40
|
Kelemen L, Galajda P, Száraz S, Ormos P. Chloride ion binding to bacteriorhodopsin at low pH: an infrared spectroscopic study. Biophys J 1999; 76:1951-8. [PMID: 10096893 PMCID: PMC1300171 DOI: 10.1016/s0006-3495(99)77354-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Bacteriorhodopsin (bR) and halorhodopsin (hR) are light-induced ion pumps in the cell membrane of Halobacterium salinarium. Under normal conditions bR is an outward proton transporter, whereas hR is an inward Cl- transporter. There is strong evidence that at very low pH and in the presence of Cl-, bR transports Cl- ions into the cell, similarly to hR. The chloride pumping activity of bR is connected to the so-called acid purple state. To account for the observed effects in bR a tentative complex counterion was suggested for the protonated Schiff base of the retinal chromophore. It would consist of three charged residues: Asp-85, Asp-212, and Arg-82. This quadruplet (including the Schiff base) would also serve as a Cl- binding site at low pH. We used Fourier transform infrared difference spectroscopy to study the structural changes during the transitions between the normal, acid blue, and acid purple states. Asp-85 and Asp-212 were shown to participate in the transitions. During the normal-to-acid blue transition, Asp-85 protonates. When the pH is further lowered in the presence of Cl-, Cl- binds and Asp-212 also protonates. The binding of Cl- and the protonation of Asp-212 occur simultaneously, but take place only when Asp-85 is already protonated. It is suggested that HCl is taken up in undissociated form in exchange for a neutral water molecule.
Collapse
Affiliation(s)
- L Kelemen
- Institute of Biophysics, Biological Research Center of the Hungarian Academy of Sciences, Szeged, H-6701 Hungary
| | | | | | | |
Collapse
|
41
|
|
42
|
Sreeramulu K, Schmidt CL, Schäfer G, Anemüller S. Studies of the electron transport chain of the euryarcheon Halobacterium salinarum: indications for a type II NADH dehydrogenase and a complex III analog. J Bioenerg Biomembr 1998; 30:443-53. [PMID: 9932647 DOI: 10.1023/a:1020538129400] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The components involved in the respiratory system of the euryarcheon Halobacterium salinarum were investigated by spectroscopic and polarographic techniques. Previous results about the cytochrome composition could be verified. However, under low oxygen tension, the expression of a d-type cytochrome was detected. Membranes exerted an NADH- and succinatecytochrome-c oxidoreductase as well as an NADH and succinate oxidase activity. These activities could be blocked by the following inhibitors: 7-jodocarboxylic acid, giving evidence for the presence of a type II NADH dehydrogenase, antimycin A, and myxothiazol, indicating the presence of a complex III analog, and the typical succinate dehydrogenase (SDH) and terminal oxidase inhibitors. Complex I inhibitors like rotenone and annonine were inactive, clearly excluding the presence of a coupled NADH dehydrogenase. In addition, no [Fe-S] resonances in the region of the NADH dehydrogenase (NDH) clusters could be observed after NADH addition. One of the terminal oxidases could be shown to act as a cytochrome-c oxidase with a Km value of 37 microM and an activation energy of 23.7 kJ/mol. The relative molecular mass of the endogenous c-type cytochrome could be determined as 14.1 kD. The complex III analog could be enriched after detergent extraction with Triton X-100 and hydroxylapatite (HTP) chromatography. The partially purified complex contained a Rieske iron-sulfur cluster, b- and c-type cytochromes, and was catalytically active in the decylubiquinone-cytochrome-c oxidoreductase assay.
Collapse
Affiliation(s)
- K Sreeramulu
- Department of Biochemistry, Gulbarga University, India
| | | | | | | |
Collapse
|
43
|
Fitter J, Verclas SA, Lechner RE, Seelert H, Dencher NA. Function and picosecond dynamics of bacteriorhodopsin in purple membrane at different lipidation and hydration. FEBS Lett 1998; 433:321-5. [PMID: 9744819 DOI: 10.1016/s0014-5793(98)00938-7] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
By neutron scattering experiments and time-resolved absorption spectroscopy we have investigated picosecond equilibrium fluctuations and the kinetics of the photocycle of bacteriorhodopsin (BR) in the purple membrane (PM). Natural PM samples composed of 75% BR (w/w) and 25% lipid (w/w) as well as delipidated PM having only 5% lipid (w/w) were measured at different levels of hydration. We observed a reduced 'flexibility', due to a diminished weight of stochastic large-amplitude motions occurring in the delipidated PM as compared to the natural PM. This effect is more pronounced for wet samples, indicating the importance of lipid hydration for protein dynamics. The reduced flexibility is accompanied by significantly larger time constants describing the decay of the M-intermediate. Therefore, a correlation between the dynamical behavior of the protein-lipid complex and BR function emerges.
Collapse
Affiliation(s)
- J Fitter
- Institut für Biochemie, TU Darmstadt, Germany.
| | | | | | | | | |
Collapse
|
44
|
Petrak MR, Hong FT. Component analysis of the fast photoelectric signal from model bacteriorhodopsin membranes. ACTA ACUST UNITED AC 1998. [DOI: 10.1016/s0302-4598(97)00068-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
45
|
Lechner RE, Fitter J, Dencher NA, Hauss T. Dehydration of biological membranes by cooling: an investigation on the purple membrane. J Mol Biol 1998; 277:593-603. [PMID: 9533882 DOI: 10.1006/jmbi.1997.1597] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The lamellar spacing dl of purple membrane (PM) multilayer systems was investigated with neutron diffraction as a function of temperature and of the level of hydration. The observed large T-dependent variations of dl indicate that PM is partially dehydrated when cooled below a "hydration water freezing point". This phenomenon is reversible, but a hysteresis is observed when PM is rehydrated upon reheating. The hydration water remaining bound to the membrane below about 240 K is non-freezing. Its amount was found to be hnf=0.24(+/-0.02) g 2H2O/g BR for all samples equilibrated at room temperature in the presence of 2H2O vapour at >/=84% r.h. It is evident, that the dehydration/rehydration behaviour of PM is strongly correlated with the temperature-dependent behaviour of the dynamical structure factor. Above the well-known "dynamical transition" announcing the onset of localized diffusive molecular motions between 190 K and 230 K, a second dynamical transition is caused by the temperature-induced rehydration of the PM starting near 255 K. This is also correlated with the deviation from a pure Arrhenius law of the rate-limiting process in the photocycle, known to occur upon cooling beyond the ice point into the same temperature region. Our results suggest that the phenomenon of dehydration and rehydration induced by cooling and reheating, respectively, is a general property of biological membranes.
Collapse
Affiliation(s)
- R E Lechner
- Hahn-Meitner-Institut/BENSC, Glienicker Strasse 100, Berlin, D-14109, Germany
| | | | | | | |
Collapse
|
46
|
Lanyi JK, Maeda A. Structural Basis of Information Transfer and Energy Transduction in Rhodopsins. Photochem Photobiol 1997. [DOI: 10.1111/j.1751-1097.1997.tb03216.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
47
|
Wang JP, Yoo SK, Song L, El-Sayed MA. Molecular Mechanism of the Differential Photoelectric Response of Bacteriorhodopsin. J Phys Chem B 1997. [DOI: 10.1021/jp962111j] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jian-Ping Wang
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
| | - Seoung-Kyo Yoo
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
| | - Li Song
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
| | - Mostafa A. El-Sayed
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
| |
Collapse
|
48
|
Scharf B, Wittenberg R, Engelhard M. Electron transfer proteins from the haloalkaliphilic archaeon Natronobacterium pharaonis: possible components of the respiratory chain include cytochrome bc and a terminal oxidase cytochrome ba3. Biochemistry 1997; 36:4471-9. [PMID: 9109654 DOI: 10.1021/bi962312d] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Natronobacterium pharaonis, an aerobic haloalkaliphilic archaebacterium, expresses high concentrations of redox proteins as do alkaliphilic eubacteria. The first redox protein characterized from N. pharaonis was halocyanin [Scharf, B., & Engelhard, M. (1993) Biochemistry 32, 12894-12900], a small blue copper protein. It is a peripheral membrane protein and is conjectured to function in a manner similar to plastocyanin. In the present work, the respiratory chain is further elucidated and the purification and characterization of the most abundant components cytochrome bc and cytochrome ba3 from the membrane fraction are described. The cytochrome bc complex consists of a 14 and an 18 kDa subunit in a 1:1 ratio, with heme c bound to the larger polypeptide. An Fe-S subunit similar to that found in eukaryotic bc complexes has not yet been identified. The second membrane complex carries two different heme groups of the ba3-type as well as copper. It contains two subunits of 36 and 40 kDa. This cytochrome ba3 binds carbon monoxide, a feature common to terminal oxidases. There is no spectroscopic evidence for a second terminal oxidase; hence, under the growth conditions chosen the respiratory chain of N. pharaonis appears to be unbranched. In addition to these cytochromes, a succinate dehydrogenase which is solubilized from the membrane by detergents was isolated. A cytochrome c which was isolated from the cytosol has an unusually high molecular weight and a redox potential of -142 mV. A second cytosolic protein, ferredoxin, was purified to homogeneity. A comparison of the redox potentials of the isolated proteins with those obtained from the native membrane allows the construction of a possible electron transfer chain.
Collapse
Affiliation(s)
- B Scharf
- Max-Planck-Institut für molekulare Physiologie, Dortmund, Germany
| | | | | |
Collapse
|
49
|
Abstract
Bacteriorhodopsin (BR), halorhodopsin (HR), and rhodopsin (Rh) all belong to the class of seven-helix membrane proteins. For BR, a structural model at atomic resolution is available; for HR, diffraction data are available only down to a resolution of 6 A in the membrane plane, and for Rh, down to 9 A. BR and HR are closely related proteins with a sequence homology of 34%, while Rh does not share any sequence homology with BR. An atomic model for HR is derived that is based on sequence alignment and the atomic model for BR and is improved by molecular dynamics simulations. The model structure obtained accounts well for the experimentally observed difference between HR and BR in the projection map, where HR exhibits a higher density in the region between helices D and E. The reason for this difference lies partially in the different side chains and partially in slightly different helix tilts. The scattering amplitudes and phases of the model structure are calculated and agree with the experimental data down to a resolution of about 8 A. If the helix positions are adopted from the projection map for HR and used as input in the model, this number improves to 7 A. Analogously, an atomic model for Rh is derived based on the atomic model for BR and subjected to molecular dynamics simulations. Optimal agreement with the experimental projection map for Rh is obtained when the entire model structure is rotated slightly about two axes in the membrane plane. The agreement with the experimental projection map is not as satisfactory as for HR, but the results indicate that even for a nonhomologous, but structurally related, protein such as Rh, an acceptable model structure can be derived from the structure of BR.
Collapse
Affiliation(s)
- M Neumüller
- Max-Planck-Institut für Biologie, Abteilung Membranbiochemie, Tübingen, Germany
| | | |
Collapse
|
50
|
Zhang D, Mauzerall D. Volume and enthalpy changes in the early steps of bacteriorhodopsin photocycle studied by time-resolved photoacoustics. Biophys J 1996; 71:381-8. [PMID: 8804620 PMCID: PMC1233488 DOI: 10.1016/s0006-3495(96)79235-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We have studied the photoinduced volume changes, energetics, and kinetics in the early steps of the bacteriorhodopsin (BR) photocycle with pulsed, time-resolved photoacoustics. Our data show that there are two volume changes. The fast volume change ( < or = 200 ns) is an expansion (2.5 +/- 0.3 A3/molecule) and is observed exclusively in the purple membrane (PM), vanishing in the 3-[(3-cholamidopropyl)-dimethylammonio] -1-propane-sulfonate-sulfonate-solubilized BR sample; the slow change (approximately 1 micros) is a volume contraction (-3.7 +/- 0.3 A3/molecule). The fast expansion is assigned to the restructuring of the aggregated BR in the PM, and the 1-micros contraction to the change in hydrogen bonding of water at Asp 212 (Kandori et al. 1995. J. Am. Chem. Soc. 117:2118-2119). The formation of the K intermediate releases most of the absorbed energy as heat, with delta Hk = -36 +/- 8 kJ/mol. The activation energy of the K --> L step is 49 +/- 6 kJ/mol, but the enthalpy change is small, -4 +/- 10 kJ/mol. On the time scale we studied, the primary photochemical kinetics, enthalpy, and volume changes are not affected by substituting the solvent D2O for H2O. Comparing data on monomeric and aggregated BR, we conclude that the functional unit for the photocycle is the BR monomer, because both the kinetics (rate constant and activation energy) and the enthalpy changes are independent of its aggregation state.
Collapse
Affiliation(s)
- D Zhang
- Rockefeller University, New York, New York 10021, USA
| | | |
Collapse
|