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Samaei A, Deshmukh SS, Protheroe C, Nyéki S, Tremblay-Ethier RA, Kálmán L. Photoactivation and conformational gating for manganese binding and oxidation in bacterial reaction centers. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148928. [PMID: 36216075 DOI: 10.1016/j.bbabio.2022.148928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 09/26/2022] [Accepted: 10/03/2022] [Indexed: 11/05/2022]
Abstract
The influence of illumination history of native bacterial reaction centers (BRCs) on the ability of binding and photo-induced oxidation of manganous ions was investigated in the pH range between 8.0 and 9.4. Binding of manganous ions to a buried site required 6 to 11-fold longer incubation periods, depending on the pH, in dark-adapted BRCs than in BRCs that were previously illuminated prior to manganese binding. The intrinsic electron transfer from the bound manganese ion to the photo-oxidized primary electron donor was found to be limited by a 2 to 5-fold slower precursor conformational step in the dark-adapted samples for the same pH range. The conformational gating could be eliminated by photoactivation, namely if the BRCs were illuminated prior to binding. Unlike in Photosystem II, photoactivation in BRCs did not involve cluster assembly. Photoactivation with manganese already bound was only possible at elevated detergent concentration. In addition, also exclusively in dark-adapted BRCs, a marked breaking point in the Arrhenius-plot was discovered around 15 °C at pH 9.4 indicating a change in the reaction mechanism, most likely caused by the change of orientation of the 2-acetyl group of the inactive bacteriochlorophyll monomer located near the manganese binding site.
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Affiliation(s)
- Ali Samaei
- Department of Physics, Concordia University, Montreal, QC, Canada
| | | | | | - Sarah Nyéki
- Department of Physics, Concordia University, Montreal, QC, Canada
| | | | - László Kálmán
- Department of Physics, Concordia University, Montreal, QC, Canada.
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2
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Knox PP, Lukashev EP, Korvatovskiy BN, Strakhovskaya MG, Makhneva ZK, Bol'shakov MA, Paschenko VZ. Disproportionate effect of cationic antiseptics on the quantum yield and fluorescence lifetime of bacteriochlorophyll molecules in the LH1-RC complex of R. rubrum chromatophores. PHOTOSYNTHESIS RESEARCH 2022; 153:103-112. [PMID: 35277801 DOI: 10.1007/s11120-022-00909-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Accepted: 02/26/2022] [Indexed: 06/14/2023]
Abstract
Photosynthetic membrane complexes of purple bacteria are convenient and informative macromolecular systems for studying the mechanisms of action of various physicochemical factors on the functioning of catalytic proteins both in an isolated state and as part of functional membranes. In this work, we studied the effect of cationic antiseptics (chlorhexidine, picloxydine, miramistin, and octenidine) on the fluorescence intensity and the efficiency of energy transfer from the light-harvesting LH1 complex to the reaction center (RC) of Rhodospirillum rubrum chromatophores. The effect of antiseptics on the fluorescence intensity and the energy transfer increased in the following order: chlorhexidine, picloxydine, miramistin, octenidine. The most pronounced changes in the intensity and lifetime of fluorescence were observed with the addition of miramistin and octenidine. At the same concentration of antiseptics, the increase in fluorescence intensity was 2-3 times higher than the increase in its lifetime. It is concluded that the addition of antiseptics decreases the efficiency of the energy migration LH1 → RC and increases the fluorescence rate constant kfl. We associate the latter with a change in the polarization of the microenvironment of bacteriochlorophyll molecules upon the addition of charged antiseptic molecules. A possible mechanism of antiseptic action on R. rubrum chromatophores is considered. This work is a continuation of the study of the effect of antiseptics on the energy transfer and fluorescence intensity in chromatophores of purple bacteria published earlier in Photosynthesis Research (Strakhovskaya et al. in Photosyn Res 147:197-209, 2021).
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Affiliation(s)
- Peter P Knox
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russian Federation, 119234
| | - Eugene P Lukashev
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russian Federation, 119234
| | - Boris N Korvatovskiy
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russian Federation, 119234
| | - Marina G Strakhovskaya
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russian Federation, 119234.
| | - Zoja K Makhneva
- Federal Research Center "Pushchino Scientific Center for Biological Research of Russian Academy of Sciences", Pushchino, Russian Federation, 142290
| | - Maxim A Bol'shakov
- Federal Research Center "Pushchino Scientific Center for Biological Research of Russian Academy of Sciences", Pushchino, Russian Federation, 142290
| | - Vladimir Z Paschenko
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russian Federation, 119234
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3
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Deshmukh SS, Kálmán L. Tuning the redox potential of the primary electron donor in bacterial reaction centers by manganese binding and light-induced structural changes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1861:148285. [PMID: 32777306 DOI: 10.1016/j.bbabio.2020.148285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 08/02/2020] [Accepted: 08/04/2020] [Indexed: 11/26/2022]
Abstract
The influence of transition metal binding on the charge storage ability of native bacterial reaction centers (BRCs) was investigated. Binding of manganous ions uniquely prevented the light-induced conformational changes that would yield to long lifetimes of the charge separated state and the drop of the redox potential of the primary electron donor (P). The lifetimes of the stable charge pair in the terminal conformations were shortened by 50-fold and 7-fold upon manganous and cupric ion binding, respectively. Nickel and zinc binding had only marginal effects. Binding of manganese not only prevented the drop of the potential of P/P+ but also elevated it by up to 117 mV depending on where the metal was binding. With variable conditions, facilitating either manganese binding or light-induced structural changes a controlled tuning of the potential of P/P+ in multiple steps was demonstrated in a range of ~200 mV without the need of a mutation or synthesis. Under the selected conditions, manganese binding was achieved without its photochemical oxidation thus, the energized but still native BRCs can be utilized in photochemistry that is not reachable with regular BRCs. A 42 Å long hydrophobic tunnel was identified that became obstructed upon manganese binding and its likely role is to deliver protons from the hydrophobic core to the surface during conformational changes.
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Affiliation(s)
| | - László Kálmán
- Department of Physics, Concordia University, Montreal, QC, Canada.
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4
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Gorka M, Cherepanov DA, Semenov AY, Golbeck JH. Control of electron transfer by protein dynamics in photosynthetic reaction centers. Crit Rev Biochem Mol Biol 2020; 55:425-468. [PMID: 32883115 DOI: 10.1080/10409238.2020.1810623] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Trehalose and glycerol are low molecular mass sugars/polyols that have found widespread use in the protection of native protein states, in both short- and long-term storage of biological materials, and as a means of understanding protein dynamics. These myriad uses are often attributed to their ability to form an amorphous glassy matrix. In glycerol, the glass is formed only at cryogenic temperatures, while in trehalose, the glass is formed at room temperature, but only upon dehydration of the sample. While much work has been carried out to elucidate a mechanistic view of how each of these matrices interact with proteins to provide stability, rarely have the effects of these two independent systems been directly compared to each other. This review aims to compile decades of research on how different glassy matrices affect two types of photosynthetic proteins: (i) the Type II bacterial reaction center from Rhodobacter sphaeroides and (ii) the Type I Photosystem I reaction center from cyanobacteria. By comparing aggregate data on electron transfer, protein structure, and protein dynamics, it appears that the effects of these two distinct matrices are remarkably similar. Both seem to cause a "tightening" of the solvation shell when in a glassy state, resulting in severely restricted conformational mobility of the protein and associated water molecules. Thus, trehalose appears to be able to mimic, at room temperature, nearly all of the effects on protein dynamics observed in low temperature glycerol glasses.
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Affiliation(s)
- Michael Gorka
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, USA
| | - Dmitry A Cherepanov
- N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Moscow, Russia.,A.N. Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Alexey Yu Semenov
- N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Moscow, Russia.,A.N. Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - John H Golbeck
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, USA.,Department of Chemistry, The Pennsylvania State University, University Park, PA, USA
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5
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Modafferi D, Zazubovich V, Kálmán L. Bound detergent molecules in bacterial reaction centers facilitate detection of tetryl explosive. PHOTOSYNTHESIS RESEARCH 2020; 145:145-157. [PMID: 32632533 DOI: 10.1007/s11120-020-00770-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 06/24/2020] [Indexed: 06/11/2023]
Abstract
Bacterial reaction centers (BRC) from Rhodobacter sphaeroides were found to accelerate, about 100-fold, the reaction between tetryl (2,4,6-trinitrophenylmethylnitramine) explosive and n-lauryl-N-N-dimethylamine-N-oxide (LDAO) that results in the formation of picric acid-like product with characteristic UV-VIS absorption spectrum with peaks at 345 and 415 nm. Moreover, this product also affects the spectra of BRC cofactors in the NIR spectral region and stabilizes the conformational changes associated with slow charge recombination. The evolution of the NIR absorption changes correlated with the kinetics of the product formation. Comparison between the wild-type and the R26 carotenoid-less strain indicates that tetryl-LDAO reaction is roughly five times faster for R26, which allows for identifying the carotenoid binding site as the optimal reaction site. Another, less-defined reaction site is located in the BRC's hydrophobic cavity. These effects are highly selective for tetryl and not observed for several other widespread nitric explosives; slowed-down charge recombination allows for distinguishing between tetryl and QB-site herbicides. The current limit of detection is in the ppb range or ~ 100 nM. Details of the molecular mechanisms of the reactions and perspectives of using these effects in bioassays or biosensors for explosives detection are also discussed.
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Affiliation(s)
- Daniel Modafferi
- Department of Physics, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, H4B 1R6, Canada
- Department of Chemical Engineering, McGill University, Montreal, QC, Canada
| | - Valter Zazubovich
- Department of Physics, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, H4B 1R6, Canada.
| | - László Kálmán
- Department of Physics, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, H4B 1R6, Canada.
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6
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In situ spectroelectrochemical investigation of a biophotoelectrode based on photoreaction centers embedded in a redox hydrogel. Electrochim Acta 2020. [DOI: 10.1016/j.electacta.2019.135190] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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7
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Giustini M, Parente M, Mallardi A, Palazzo G. Effect of ionic strength on intra-protein electron transfer reactions: The case study of charge recombination within the bacterial reaction center. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1541-1549. [PMID: 27297026 DOI: 10.1016/j.bbabio.2016.06.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 06/06/2016] [Accepted: 06/09/2016] [Indexed: 11/27/2022]
Abstract
It is a common believe that intra-protein electron transfer (ET) involving reactants and products that are overall electroneutral are not influenced by the ions of the surrounding solution. The results presented here show an electrostatic coupling between the ionic atmosphere surrounding a membrane protein (the reaction center (RC) from the photosynthetic bacterium Rhodobacter sphaeroides) and two very different intra-protein ET processes taking place within it. Specifically we have studied the effect of salt concentration on: i) the kinetics of the charge recombination between the reduced primary quinone acceptor QA(-) and the primary photoxidized donor P(+); ii) the thermodynamic equilibrium (QA(-)↔QB(-)) for the ET between QA(-) and the secondary quinone acceptor QB. A distinctive point of this investigation is that reactants and products are overall electroneutral. The protein electrostatics has been described adopting the lowest level of complexity sufficient to grasp the experimental phenomenology and the impact of salt on the relative free energy level of reactants and products has been evaluated according to suitable thermodynamic cycles. The ionic strength effect was found to be independent on the ion nature for P(+)QA(-) charge recombination where the leading electrostatic term was the dipole moment. In the case of the QA(-)↔QB(-) equilibrium, the relative stability of QA(-) and QB(-) was found to depend on the salt concentration in a fashion that is different for chaotropic and kosmotropic ions. In such a case both dipole moment and quadrupole moments of the RC must be considered.
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Affiliation(s)
- Mauro Giustini
- Chemistry Department, University of Rome "La Sapienza", Italy; CSGI (Center for Colloid and Surface Science), c/o Dept. Chemistry, via Orabona 4, 70125 Bari, Italy.
| | - Matteo Parente
- Dutch Institute for Fundamental Energy Research (DIFFER), De Zaale 20, 5612, AJ, Eindhoven, The Netherlands
| | - Antonia Mallardi
- CNR-IPCF, Istituto per i processi chimico fisici, c/o Dept. Chemistry, via Orabona 4, 70125 Bari, Italy
| | - Gerardo Palazzo
- Chemistry Department, University of Bari, via Orabona 4, 70125 Bari, Italy; CSGI (Center for Colloid and Surface Science), c/o Dept. Chemistry, via Orabona 4, 70125 Bari, Italy.
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8
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Malferrari M, Turina P, Francia F, Mezzetti A, Leibl W, Venturoli G. Dehydration affects the electronic structure of the primary electron donor in bacterial photosynthetic reaction centers: evidence from visible-NIR and light-induced difference FTIR spectroscopy. Photochem Photobiol Sci 2015; 14:238-51. [PMID: 25188921 DOI: 10.1039/c4pp00245h] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The photosynthetic reaction center (RC) is a membrane pigment-protein complex that catalyzes the initial charge separation reactions of photosynthesis. Following photoexcitation, the RC undergoes conformational relaxations which stabilize the charge-separated state. Dehydration of the complex inhibits its conformational dynamics, providing a useful tool to gain insights into the relaxational processes. We analyzed the effects of dehydration on the electronic structure of the primary electron donor P, as probed by visible-NIR and light-induced FTIR difference spectroscopy, in RC films equilibrated at different relative humidities r. Previous FTIR and ENDOR spectroscopic studies revealed that P, an excitonically coupled dimer of bacteriochlorophylls, can be switched between two conformations, P866 and P850, which differ in the extent of delocalization of the unpaired electron between the two bacteriochlorophyll moieties (PL and PM) of the photo-oxidized radical P(+). We found that dehydration (at r = 11%) shifts the optical Qy band of P from 866 to 850-845 nm, a large part of the effect occurring already at r = 76%. Such a dehydration weakens light-induced difference FTIR marker bands, which probe the delocalization of charge distribution within the P(+) dimer (the electronic band of P(+) at 2700 cm(-1), and the associated phase-phonon vibrational modes at around 1300, 1480, and 1550 cm(-1)). From the analysis of the P(+) keto C[double bond, length as m-dash]O bands at 1703 and 1713-15 cm(-1), we inferred that dehydration induces a stronger localization of the unpaired electron on PL(+). The observed charge redistribution is discussed in relation to the dielectric relaxation of the photoexcited RC on a long (10(2) s) time scale.
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Affiliation(s)
- Marco Malferrari
- Dipartimento di Farmacia e Biotecnologie, FaBiT, Università di Bologna, Bologna, Italy.
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9
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Swainsbury DJK, Scheidelaar S, van Grondelle R, Killian JA, Jones MR. Bacterial reaction centers purified with styrene maleic acid copolymer retain native membrane functional properties and display enhanced stability. Angew Chem Int Ed Engl 2014; 53:11803-7. [PMID: 25212490 PMCID: PMC4271668 DOI: 10.1002/anie.201406412] [Citation(s) in RCA: 115] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 08/05/2014] [Indexed: 12/15/2022]
Abstract
Integral membrane proteins often present daunting challenges for biophysical characterization, a fundamental issue being how to select a surfactant that will optimally preserve the individual structure and functional properties of a given membrane protein. Bacterial reaction centers offer a rare opportunity to compare the properties of an integral membrane protein in different artificial lipid/surfactant environments with those in the native bilayer. Here, we demonstrate that reaction centers purified using a styrene maleic acid copolymer remain associated with a complement of native lipids and do not display the modified functional properties that typically result from detergent solubilization. Direct comparisons show that reaction centers are more stable in this copolymer/lipid environment than in a detergent micelle or even in the native membrane, suggesting a promising new route to exploitation of such photovoltaic integral membrane proteins in device applications.
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Affiliation(s)
- David J K Swainsbury
- School of Biochemistry, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD (UK)
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10
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Swainsbury DJK, Scheidelaar S, van Grondelle R, Killian JA, Jones MR. Bacterial Reaction Centers Purified with Styrene Maleic Acid Copolymer Retain Native Membrane Functional Properties and Display Enhanced Stability. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201406412] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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11
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The binding of quinone to the photosynthetic reaction centers: kinetics and thermodynamics of reactions occurring at the QB-site in zwitterionic and anionic liposomes. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2014; 43:301-15. [PMID: 24824111 DOI: 10.1007/s00249-014-0963-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 04/07/2014] [Accepted: 04/25/2014] [Indexed: 12/29/2022]
Abstract
Liposomes represent a versatile biomimetic environment for studying the interaction between integral membrane proteins and hydrophobic ligands. In this paper, the quinone binding to the QB-site of the photosynthetic reaction centers (RC) from Rhodobacter sphaeroides has been investigated in liposomes prepared with either the zwitterionic phosphatidylcholine (PC) or the negatively charged phosphatidylglycerol (PG) to highlight the role of the different phospholipid polar heads. Quinone binding (K Q) and interquinone electron transfer (L AB) equilibrium constants in the two type of liposomes were obtained by charge recombination reaction of QB-depleted RC in the presence of increasing amounts of ubiquinone-10 over the temperature interval 6-35 °C. The kinetic of the charge recombination reactions has been fitted by numerically solving the ordinary differential equations set associated with a detailed kinetic scheme involving electron transfer reactions coupled with quinone release and uptake. The entire set of traces at each temperature was accurately fitted using the sole quinone release constants (both in a neutral and a charge separated state) as adjustable parameters. The temperature dependence of the quinone exchange rate at the QB-site was, hence, obtained. It was found that the quinone exchange regime was always fast for PC while it switched from slow to fast in PG as the temperature rose above 20 °C. A new method was introduced in this paper for the evaluation of constant K Q using the area underneath the charge recombination traces as the indicator of the amount of quinone bound to the QB-site.
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12
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Krasilnikov PM. Problems of the theory of electron transfer in biological systems. Biophysics (Nagoya-shi) 2014. [DOI: 10.1134/s0006350914010059] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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13
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Eisenmayer TJ, Lasave JA, Monti A, de Groot HJM, Buda F. Proton Displacements Coupled to Primary Electron Transfer in the Rhodobacter sphaeroides Reaction Center. J Phys Chem B 2013; 117:11162-8. [DOI: 10.1021/jp401195t] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Thomas J. Eisenmayer
- Leiden Institute
of Chemistry, Leiden University, Einsteinweg
55, P.O. Box 9502, 2300
RA Leiden, The Netherlands
| | - Jorge A. Lasave
- Instituto de Física Rosario (UNR-CONICET), 27 de Febrero 210 bis, 2000,
Rosario, Argentina
| | - Adriano Monti
- Leiden Institute
of Chemistry, Leiden University, Einsteinweg
55, P.O. Box 9502, 2300
RA Leiden, The Netherlands
| | - Huub J. M. de Groot
- Leiden Institute
of Chemistry, Leiden University, Einsteinweg
55, P.O. Box 9502, 2300
RA Leiden, The Netherlands
| | - Francesco Buda
- Leiden Institute
of Chemistry, Leiden University, Einsteinweg
55, P.O. Box 9502, 2300
RA Leiden, The Netherlands
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Caputo GA. Analyzing the effects of hydrophobic mismatch on transmembrane α-helices using tryptophan fluorescence spectroscopy. Methods Mol Biol 2013; 1063:95-116. [PMID: 23975773 DOI: 10.1007/978-1-62703-583-5_5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Hydrophobic matching between transmembrane protein segments and the lipid bilayer in which they are embedded is a significant factor in the behavior and orientation of such transmembrane segments. The condition of hydrophobic mismatch occurs when the hydrophobic thickness of a lipid bilayer is significantly different than the length of the membrane spanning segment of a protein, resulting in a mismatch. This mismatch can result in altered function of proteins as well as nonnative structural arrangements including effects on transmembrane α-helix tilt angles, oligomerization state, and/or the formation of non-transmembrane topographies. Here, a fluorescence-based protocol is described for testing model transmembrane α-helices and their sensitivity to hydrophobic mismatch by measuring the propensity of these helices to form non-transmembrane structures. Overall, good hydrophobic matching between the bilayer and transmembrane segments is an important factor that must be considered when designing membrane proteins or peptides.
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Affiliation(s)
- Gregory A Caputo
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ, USA
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15
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Deshmukh SS, Tang K, Kálmán L. Lipid binding to the carotenoid binding site in photosynthetic reaction centers. J Am Chem Soc 2011; 133:16309-16. [PMID: 21894992 DOI: 10.1021/ja207750z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Lipid binding to the carotenoid binding site near the inactive bacteriochlorophyll monomer was probed in the reaction centers of carotenoid-less mutant, R-26 from Rhodobacter sphaeroides. Recently, a marked light-induced change of the local dielectric constant in the vicinity of the inactive bacteriochlorophyll monomer was reported in wild type that was attributed to structural changes that ultimately lengthened the lifetime of the charge-separated state by 3 orders of magnitude (Deshmukh, S. S.; Williams, J. C.; Allen, J. P.; Kalman, L. Biochemistry 2011, 50, 340). Here in the R-26 reaction centers, the combination of light-induced structural changes and lipid binding resulted in a 5 orders of magnitude increase in the lifetime of the charge-separated state involving the oxidized dimer and the reduced primary quinone in proteoliposomes. Only saturated phospholipids with fatty acid chains of 12 and 14 carbon atoms long were bound successfully at 8 °C by cooling the reaction center protein slowly from room temperature. In addition to reporting a dramatic increase of the lifetime of the charge-separated state at physiologically relevant temperatures, this study reveals a novel lipid binding site in photosynthetic reaction center. These results shed light on a new potential application of the reaction center in energy storage as a light-driven biocapacitor since the charges separated by ∼30 Å in a low-dielectric medium can be prevented from recombination for hours.
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Affiliation(s)
- Sasmit S Deshmukh
- Department of Physics, Concordia University, Montreal, Quebec H4B 1R6, Canada
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