The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform

Mordechai Sheves - One of the best experts on this subject based on the ideXlab platform.

  • spin controlled photoluminescence in hybrid nanoparticles purple membrane system
    ACS Nano, 2016
    Co-Authors: Nirit Kantoruriel, Mordechai Sheves, Noga Friedman, Sansa Dutta, Debabrata Mishra, Ron Naaman
    Abstract:

    Spin-dependent photoluminescence (PL) quenching of CdSe nanoparticles (NPs) has been explored in the hybrid system of CdSe NP purple membrane, wild-type bacteriorhodopsin (bR) thin film on a ferromagnetic (Ni-alloy) substrate. A significant change in the PL intensity from the CdSe NPs has been observed when spin-specific charge transfer occurs between the Retinal and the magnetic substrate. This feature completely disappears in a bR apo membrane (wild-type bacteriorhodopsin in which the Retinal Protein covalent bond was cleaved), a bacteriorhodopsin mutant (D96N), and a bacteriorhodopsin bearing a locked Retinal chromophore (isomerization of the crucial C13═C14 Retinal double bond was prevented by inserting a ring spanning this bond). The extent of spin-dependent PL quenching of the CdSe NPs depends on the absorption of the Retinal, embedded in wild-type bacteriorhodopsin. Our result suggests that spin-dependent charge transfer between the Retinal and the substrate controls the PL intensity from the NPs.

  • conjugated cofactor enables efficient temperature independent electronic transport across 6 nm long halorhodopsin
    Journal of the American Chemical Society, 2015
    Co-Authors: Sabyasachi Mukhopadhyay, Mordechai Sheves, Sansa Dutta, Israel Pecht, David Cahen
    Abstract:

    We observe temperature-independent electron transport, characteristic of tunneling across a ∼6 nm thick Halorhodopsin (phR) monolayer. phR contains both Retinal and a carotenoid, bacterioruberin, as cofactors, in a trimeric Protein-chromophore complex. This finding is unusual because for conjugated oligo-imine molecular wires a transition from temperature-independent to -dependent electron transport, ETp, was reported at ∼4 nm wire length. In the ∼6 nm long phR, the ∼4 nm 50-carbon conjugated bacterioruberin is bound parallel to the α-helices of the peptide backbone. This places bacterioruberin’s ends proximal to the two electrodes that contact the Protein; thus, coupling to these electrodes may facilitate the activation-less current across the contacts. Oxidation of bacterioruberin eliminates its conjugation, causing the ETp to become temperature dependent (>180 K). Remarkably, even elimination of the Retinal-Protein covalent bond, with the fully conjugated bacterioruberin still present, leads to tempera...

  • probing ultrafast photochemistry of Retinal Proteins in the near ir bacteriorhodopsin and anabaena sensory rhodopsin vs Retinal protonated schiff base in solution
    Journal of Physical Chemistry B, 2013
    Co-Authors: Amir Wand, Mordechai Sheves, Noga Friedman, Barry Loevsky, Sanford Ruhman
    Abstract:

    Photochemistry of bacteriorhodopsin (bR), anabaena sensory rhodopsin (ASR), and all-trans Retinal protonated Schiff base (RPSB) in ethanol is followed with femtosecond pump–hyperspectral near-IR (NIR) probe spectroscopy. This is the first systematic probing of Retinal Protein photochemistry in this spectral range. Stimulated emission of the Proteins is demonstrated to extend deep into the NIR, and to decay on the same characteristic time scales previously determined by visible probing. No signs of a transient NIR absorption band above λpr > 1.3 μm, which was recently reported and is verified here for the RPSB in solution, is observed in either Protein. This discrepancy demonstrates that the Protein surroundings change photochemical traits of the chromophore significantly, inducing changes either in the energies or couplings of photochemically relevant electronic excited states. In addition, low-frequency and heavily damped spectral modulations are observed in the NIR signals of all three systems up to 1.4...

  • Retinal β ionone ring salinixanthin interactions in xanthorhodopsin a study using artificial pigments
    Biochemistry, 2013
    Co-Authors: Elena Smolensky Koganov, Amiram Hirshfeld, Mordechai Sheves
    Abstract:

    Xanthorhodopsin (xR) is a Retinal Protein that contains, in addition to the Retinal chromophore, a carotenoid (salinixanthin) that functions as a light-harvesting antenna [Balashov, S. P., et al. (2005) Science 309, 2061–2064]. The center–center distance between the two polyene chains is 12–13 A, but the distance between the two rings of Retinal and salinixanthin is surprisingly small (∼5 A) with an angle of ∼45° [Luecke, H., et al. (2008) Proc. Natl. Acad. Sci. U.S.A. 105, 16561–16565]. We aimed to clarify the role of the β-ionone ring in the binding of Retinal to apo-xR, as well as a possible role that the β-ionone ring plays in fixation of the salinixanthin 4-keto ring. The binding of native Retinal and series of synthetic Retinal analogues modified in the β-ionone ring to apo-xR was monitored by absorption and circular dichroism (CD) spectroscopies. The results indicate that the β-ionone ring modification significantly affected formation of the Retinal–Protein covalent bond as well as the pigment abso...

  • Shedding New Light on Retinal Protein Photochemistry
    Annual review of physical chemistry, 2013
    Co-Authors: Amir Wand, Mordechai Sheves, Itay Gdor, Jingyi Zhu, Sanford Ruhman
    Abstract:

    The ultrafast spectroscopic investigation of novel Retinal Proteins challenges existing notions concerning the course of primary events in these natural photoreceptors. We review two illustrations here. The first demonstrates that changes in the initial Retinal configuration can alter the duration of photochemistry by nearly an order of magnitude in Anabaena sensory rhodopsin, making it as rapid as the ballistic photoisomerization in visual pigments. This prompted a reinvestigation of the much studied bacteriorhodopsin, leading to a similar trend as well, contrary to earlier reports. The second involves the study of xanthorhodopsin, an archaeal proton pump that includes an attached light-harvesting carotenoid. Pump-probe experiments demonstrate the efficient transfer of energy from carotenoid to Retinal, providing a first glimpse at a cooperative multichromophore function, which is probably characteristic of many other Proteins as well. Finally, we discuss measures required to advance our knowledge from kinetics to mode-specific dynamics concerning this expanding family of biological photoreceptors.

Martin Engelhard - One of the best experts on this subject based on the ideXlab platform.

  • Retinal Protein interactions in halorhodopsin from natronomonas pharaonis binding and Retinal thermal isomerization catalysis
    Journal of Molecular Biology, 2009
    Co-Authors: Tushar Kanti Maiti, Martin Engelhard, Mordechai Sheves
    Abstract:

    Abstract Halorhodopsin from Natronomonas pharaonis (NpHR) is a member of the Retinal Protein group and serves as a light-driven chloride pump in which chloride ions are transported through the membrane following light absorption by the Retinal chromophore. In this study, we examined two main issues: (1) factors controlling the binding of the Retinal chromophore to the NpHR opsin and (2) the ability of the NpHR opsin to catalyze the thermal isomerization of Retinal isomers. We have revealed that the reconstitution process of pharaonis HR (NpHR) pigment from its apoProtein and all- trans Retinal depends on the pH, and the process has a p K a of 5.8 ± 0.1. It was proposed that this p K a is associated with the p K a of the lysine residue that binds the Retinal chromophore (Lys256). The pigment formation is regulated by the concentration of sodium chloride, and the maximum yield was observed at 3.7 M NaCl. The low yield of pigment in a lower concentration of NaCl ( cis Retinal and 9- cis Retinal owing to the thermal isomerization of these Retinal isomers to all- trans Retinal. The isomerization rate depends on the pH, and it is faster at a higher pH. The p K a value of the isomerization process is similar to the p K a of the binding process of these Retinals, which suggests that Lys256 is also involved in the isomerization process. The isomerization is independent of the sodium chloride concentration. However, in the absence of sodium chloride, the apoProtein adopts such a conformation, which does not prevent the isomerization of Retinal, but it prevents a covalent bond formation with the lysine residue. The rate and the thermodynamic parameter analysis of the Retinal isomerization by NpHR apoProtein led to the conclusion that the apomembrane catalyzes the isomerization via a triplet mechanism.

  • Retinal–Protein Interactions in Halorhodopsin from Natronomonas pharaonis: Binding and Retinal Thermal Isomerization Catalysis
    Journal of Molecular Biology, 2009
    Co-Authors: Tushar Kanti Maiti, Martin Engelhard, Mordechai Sheves
    Abstract:

    Abstract Halorhodopsin from Natronomonas pharaonis (NpHR) is a member of the Retinal Protein group and serves as a light-driven chloride pump in which chloride ions are transported through the membrane following light absorption by the Retinal chromophore. In this study, we examined two main issues: (1) factors controlling the binding of the Retinal chromophore to the NpHR opsin and (2) the ability of the NpHR opsin to catalyze the thermal isomerization of Retinal isomers. We have revealed that the reconstitution process of pharaonis HR (NpHR) pigment from its apoProtein and all- trans Retinal depends on the pH, and the process has a p K a of 5.8 ± 0.1. It was proposed that this p K a is associated with the p K a of the lysine residue that binds the Retinal chromophore (Lys256). The pigment formation is regulated by the concentration of sodium chloride, and the maximum yield was observed at 3.7 M NaCl. The low yield of pigment in a lower concentration of NaCl ( cis Retinal and 9- cis Retinal owing to the thermal isomerization of these Retinal isomers to all- trans Retinal. The isomerization rate depends on the pH, and it is faster at a higher pH. The p K a value of the isomerization process is similar to the p K a of the binding process of these Retinals, which suggests that Lys256 is also involved in the isomerization process. The isomerization is independent of the sodium chloride concentration. However, in the absence of sodium chloride, the apoProtein adopts such a conformation, which does not prevent the isomerization of Retinal, but it prevents a covalent bond formation with the lysine residue. The rate and the thermodynamic parameter analysis of the Retinal isomerization by NpHR apoProtein led to the conclusion that the apomembrane catalyzes the isomerization via a triplet mechanism.

  • Retinal–Protein Interactions in Halorhodopsin from Natronomonas pharaonis: Binding and Retinal Thermal Isomerization Catalysis
    Journal of molecular biology, 2009
    Co-Authors: Tushar Kanti Maiti, Martin Engelhard, Mordechai Sheves
    Abstract:

    Halorhodopsin from Natronomonas pharaonis (NpHR) is a member of the Retinal Protein group and serves as a light-driven chloride pump in which chloride ions are transported through the membrane following light absorption by the Retinal chromophore. In this study, we examined two main issues: (1) factors controlling the binding of the Retinal chromophore to the NpHR opsin and (2) the ability of the NpHR opsin to catalyze the thermal isomerization of Retinal isomers. We have revealed that the reconstitution process of pharaonis HR (NpHR) pigment from its apoProtein and all-trans Retinal depends on the pH, and the process has a pK(a) of 5.8+/-0.1. It was proposed that this pK(a) is associated with the pK(a) of the lysine residue that binds the Retinal chromophore (Lys256). The pigment formation is regulated by the concentration of sodium chloride, and the maximum yield was observed at 3.7 M NaCl. The low yield of pigment in a lower concentration of NaCl (

  • Primary reactions of sensory rhodopsins
    Proceedings of the National Academy of Sciences of the United States of America, 2001
    Co-Authors: I. G. Lutz, Martin Engelhard, Dieter Oesterhelt, A. Sieg, A. A. Wegener, I. Boche, M. Otsuka, Josef Wachtveitl, Wolfgang Zinth
    Abstract:

    The first steps in the photocycles of the archaeal photoreceptor Proteins sensory rhodopsin (SR) I and II from Halobacterium salinarum and SRII from Natronobacterium pharaonis have been studied by ultrafast pump/probe spectroscopy and steady-state fluorescence spectroscopy. The data for both species of the blue-light receptor SRII suggests that their primary reactions are nearly analogous with a fast decay of the excited electronic state in 300–400 fs and a transition between two red-shifted product states in 4–5 ps. Thus SRII behaves similarly to bacteriorhodopsin. In contrast for SRI at pH 6.0, which absorbs in the orange part of the spectrum, a strongly increased fluorescence quantum yield and a drastically slower and biexponential decay of the excited electronic state occurring on the picosecond time scale (5 ps and 33 ps) is observed. The results suggest that the primary reactions are controlled by the charge distribution in the vicinity of the Schiff base and demonstrate that there is no direct connection between absorption properties and reaction dynamics for the Retinal Protein family.

  • the primary structure of sensory rhodopsin ii a member of an additional Retinal Protein subgroup is coexpressed with its transducer the halobacterial transducer of rhodopsin ii
    Proceedings of the National Academy of Sciences of the United States of America, 1995
    Co-Authors: Ralf Seidel, Dieter Oesterhelt, Birgit E Scharf, Mathias Gautel, Karl Kleine, Martin Engelhard
    Abstract:

    Abstract The blue-light receptor genes (sopII) of sensory rhodopsin (SR) II were cloned from two species, the halophilic bacteria Haloarcula vallismortis (vSR-II) and Natronobacterium pharaonis (pSR-II). Upstream of both sopII gene loci, sequences corresponding to the halobacterial transducer of rhodopsin (Htr) II were recognized. In N. pharaonis, psopII and phtrII are transcribed as a single transcript. Comparison of the amino acid sequences of vHtr-II and pHtr-II with Htr-I and the chemotactic methyl-accepting Proteins from Escherichia coli revealed considerable identities in the signal domain and methyl-accepting sites. Similarities with Htr-I in Halobacterium salinarium suggest a common principle in the phototaxis of extreme halophiles. Alignment of all known Retinal Protein sequences from Archaea identifies both SR-IIs as an additional subgroup of the family. Positions defining the Retinal binding site are usually identical with the exception of Met-118 (numbering is according to the bacteriorhodopsin sequence), which might explain the typical blue color shift of SR-II to approximately 490 nm. In archaeal Retinal Proteins, the function can be deduced from amino acids in positions 85 and 96. Proton pumps are characterized by Asp-85 and Asp-96; chloride pumps by Thr-85 and Ala-96; and sensors by Asp-85 and Tyr-96 or Phe-96.

Dieter Oesterhelt - One of the best experts on this subject based on the ideXlab platform.

  • a small basic Protein from the brz brb operon is involved in regulation of bop transcription in halobacterium salinarum
    BMC Molecular Biology, 2011
    Co-Authors: Valery Tarasov, Rita Schwaiger, Katarina Furtwangler, Mike Dyallsmith, Dieter Oesterhelt
    Abstract:

    Background The halophilic archaeon Halobacterium salinarum expresses bacteriorhodopsin, a Retinal-Protein that allows photosynthetic growth. Transcription of the bop (b acterioop sin) gene is controlled by two transcription factors, Bat and Brz that induce bop when cells are grown anaerobically and under light.

  • mpct is the transducer for membrane potential changes in halobacterium salinarum
    Molecular Microbiology, 2005
    Co-Authors: Matthias Koch, Dieter Oesterhelt
    Abstract:

    : In Halobacterium salinarum mutants containing either of the light-driven ion pumps bacteriorhodopsin (H(+)) or halorhodopsin (Cl(-)) as their only Retinal Protein, a decrease of irradiance in the absence of respiration causes a phototactic response. The conversion of the causal event, a decrease of proton motive force across the cell membrane, into a reversal of flagellar motor rotational direction was expected to involve a transducer. Via deletion analysis of all 18 known and putative halobacterial transducer (htr) genes, we found that Htr14, a methylatable membrane-bound transducer lacking an extracellular domain, mediates the biological response, which includes adaptive methylation. Based on a minimal stimulus length of 200 ms and the determined cytoplasmic buffering capacity, we conclude that the change in the membrane potential (DeltaPsi), and not that of the internal pH, is the signal-generating event. Htr14 was therefore renamed to Membrane potential change Transducer, or MpcT. It is the first transducer for which the causative stimulus could be narrowed to a change in DeltaPsi, as opposed to a change in pH or cellular redox state.

  • Primary reactions of sensory rhodopsins
    Proceedings of the National Academy of Sciences of the United States of America, 2001
    Co-Authors: I. G. Lutz, Martin Engelhard, Dieter Oesterhelt, A. Sieg, A. A. Wegener, I. Boche, M. Otsuka, Josef Wachtveitl, Wolfgang Zinth
    Abstract:

    The first steps in the photocycles of the archaeal photoreceptor Proteins sensory rhodopsin (SR) I and II from Halobacterium salinarum and SRII from Natronobacterium pharaonis have been studied by ultrafast pump/probe spectroscopy and steady-state fluorescence spectroscopy. The data for both species of the blue-light receptor SRII suggests that their primary reactions are nearly analogous with a fast decay of the excited electronic state in 300–400 fs and a transition between two red-shifted product states in 4–5 ps. Thus SRII behaves similarly to bacteriorhodopsin. In contrast for SRI at pH 6.0, which absorbs in the orange part of the spectrum, a strongly increased fluorescence quantum yield and a drastically slower and biexponential decay of the excited electronic state occurring on the picosecond time scale (5 ps and 33 ps) is observed. The results suggest that the primary reactions are controlled by the charge distribution in the vicinity of the Schiff base and demonstrate that there is no direct connection between absorption properties and reaction dynamics for the Retinal Protein family.

  • the photoreceptor sensory rhodopsin i as a two photon driven proton pump
    Proceedings of the National Academy of Sciences of the United States of America, 1995
    Co-Authors: Ulrich Haupts, Christina Haupts, Dieter Oesterhelt
    Abstract:

    Abstract Proton translocation experiments with intact cells of Halobacterium salinarium overproducing sensory rhodopsin I (SRI) revealed transport activity of SRI in a two-photon process. The vectoriality of proton translocation depends on pH, being outwardly directed above, and inwardly directed below, pH 5.7. Activation of the transport cycle requires excitation of the initial dark state of SRI, SRI590, to form the intermediate SRI380. Action spectra identify the photocycle intermediates SRI380 and SRI520 as the two photochemically reactive species in the outwardly directed transport process. As shown by flash photolysis experiments, SRI520 undergoes a so-far unknown photochemical reaction to SRI380 with a half-time of <200 micros. Mutation of SRI residue Asp-76, the residue which is equivalent to the proton acceptor Asp-85 in bacteriorhodopsin, to asparagine leads to inactivation of proton translocation. This demonstrates that the underlying mechanisms of proton transport in both Retinal Proteins share similar features. However, SRI is to our knowledge the first case where photochemical reactions between two thermally unstable photoproducts of a Retinal Protein constitute a catalytic ion transport cycle.

  • the primary structure of sensory rhodopsin ii a member of an additional Retinal Protein subgroup is coexpressed with its transducer the halobacterial transducer of rhodopsin ii
    Proceedings of the National Academy of Sciences of the United States of America, 1995
    Co-Authors: Ralf Seidel, Dieter Oesterhelt, Birgit E Scharf, Mathias Gautel, Karl Kleine, Martin Engelhard
    Abstract:

    Abstract The blue-light receptor genes (sopII) of sensory rhodopsin (SR) II were cloned from two species, the halophilic bacteria Haloarcula vallismortis (vSR-II) and Natronobacterium pharaonis (pSR-II). Upstream of both sopII gene loci, sequences corresponding to the halobacterial transducer of rhodopsin (Htr) II were recognized. In N. pharaonis, psopII and phtrII are transcribed as a single transcript. Comparison of the amino acid sequences of vHtr-II and pHtr-II with Htr-I and the chemotactic methyl-accepting Proteins from Escherichia coli revealed considerable identities in the signal domain and methyl-accepting sites. Similarities with Htr-I in Halobacterium salinarium suggest a common principle in the phototaxis of extreme halophiles. Alignment of all known Retinal Protein sequences from Archaea identifies both SR-IIs as an additional subgroup of the family. Positions defining the Retinal binding site are usually identical with the exception of Met-118 (numbering is according to the bacteriorhodopsin sequence), which might explain the typical blue color shift of SR-II to approximately 490 nm. In archaeal Retinal Proteins, the function can be deduced from amino acids in positions 85 and 96. Proton pumps are characterized by Asp-85 and Asp-96; chloride pumps by Thr-85 and Ala-96; and sensors by Asp-85 and Tyr-96 or Phe-96.

Sanford Ruhman - One of the best experts on this subject based on the ideXlab platform.

  • ultrafast photochemistry of anabaena sensory rhodopsin experiment and theory
    Biochimica et Biophysica Acta, 2014
    Co-Authors: Igor Schapiro, Sanford Ruhman
    Abstract:

    Abstract Light induced isomerization of the Retinal chromophore activates biological function in all Retinal Protein (RP) driving processes such as ion-pumping, vertebrate vision and phototaxis in organisms as primitive as archea, or as complex as mammals. This process and its consecutive reactions have been the focus of experimental and theoretical research for decades. The aim of this review is to demonstrate how the experimental and theoretical research efforts can now be combined to reach a more comprehensive understanding of the excited state process on the molecular level. Using the Anabaena Sensory Rhodopsin as an example we will show how contemporary time-resolved spectroscopy and recently implemented excited state QM/MM methods consistently describe photochemistry in Retinal Proteins. This article is part of a Special Issue entitled: Retinal Proteins — You can teach an old dog new tricks.

  • probing ultrafast photochemistry of Retinal Proteins in the near ir bacteriorhodopsin and anabaena sensory rhodopsin vs Retinal protonated schiff base in solution
    Journal of Physical Chemistry B, 2013
    Co-Authors: Amir Wand, Mordechai Sheves, Noga Friedman, Barry Loevsky, Sanford Ruhman
    Abstract:

    Photochemistry of bacteriorhodopsin (bR), anabaena sensory rhodopsin (ASR), and all-trans Retinal protonated Schiff base (RPSB) in ethanol is followed with femtosecond pump–hyperspectral near-IR (NIR) probe spectroscopy. This is the first systematic probing of Retinal Protein photochemistry in this spectral range. Stimulated emission of the Proteins is demonstrated to extend deep into the NIR, and to decay on the same characteristic time scales previously determined by visible probing. No signs of a transient NIR absorption band above λpr > 1.3 μm, which was recently reported and is verified here for the RPSB in solution, is observed in either Protein. This discrepancy demonstrates that the Protein surroundings change photochemical traits of the chromophore significantly, inducing changes either in the energies or couplings of photochemically relevant electronic excited states. In addition, low-frequency and heavily damped spectral modulations are observed in the NIR signals of all three systems up to 1.4...

  • Shedding New Light on Retinal Protein Photochemistry
    Annual review of physical chemistry, 2013
    Co-Authors: Amir Wand, Mordechai Sheves, Itay Gdor, Jingyi Zhu, Sanford Ruhman
    Abstract:

    The ultrafast spectroscopic investigation of novel Retinal Proteins challenges existing notions concerning the course of primary events in these natural photoreceptors. We review two illustrations here. The first demonstrates that changes in the initial Retinal configuration can alter the duration of photochemistry by nearly an order of magnitude in Anabaena sensory rhodopsin, making it as rapid as the ballistic photoisomerization in visual pigments. This prompted a reinvestigation of the much studied bacteriorhodopsin, leading to a similar trend as well, contrary to earlier reports. The second involves the study of xanthorhodopsin, an archaeal proton pump that includes an attached light-harvesting carotenoid. Pump-probe experiments demonstrate the efficient transfer of energy from carotenoid to Retinal, providing a first glimpse at a cooperative multichromophore function, which is probably characteristic of many other Proteins as well. Finally, we discuss measures required to advance our knowledge from kinetics to mode-specific dynamics concerning this expanding family of biological photoreceptors.

  • A new spectral window on Retinal Protein photochemistry.
    Journal of the American Chemical Society, 2011
    Co-Authors: Boris Loevsky, Mordechai Sheves, Amir Wand, Oshrat Bismuth, Noga Friedman, Sanford Ruhman
    Abstract:

    A VIS pump/hyperspectral NIR probe study of all-trans-Retinal protonated Schiff base (RPSB) in ethanol is presented. Upon irradiation, a short-lived absorption band covers the recorded range of λ = 1−2 μm. It decays to reveal the tail of S1 emission at λ < 1.3 μm, along with a residual absorption at longer wavelengths, both of which decay with the known kinetics of internal conversion to S0. The existence of this hitherto unrecorded excited-state absorption deep in the NIR will require a revision of current models for RPSB electronic structure. The phenomenological similarity of these observations with ultrafast NIR studies of carotenoids raises the question of whether three, and not two, electronic states participate in RPSB photochemistry as well. The relevance of these observations to Retinal Protein photochemistry is discussed.

  • Opening a New Spectral Window on Retinal Protein Photochemistry
    International Conference on Ultrafast Phenomena, 2010
    Co-Authors: Boris Loevsky, Mordechai Sheves, Amir Wand, Oshrat Bismuth, Noga Friedman, Sanford Ruhman
    Abstract:

    Probing the spectroscopy of the active chromophore in Retinal Proteins in the NIR for the first time shows new absorption features which support a three-state model for the photochemical dynamics of Retinal Proteins.

J K Lanyi - One of the best experts on this subject based on the ideXlab platform.

  • ESR — A Retinal Protein with unusual properties from Exiguobacterium sibiricum
    Biochemistry (Moscow), 2015
    Co-Authors: L E Petrovskaya, S P Balashov, E P Lukashev, E S Imasheva, I Yu Gushchin, A K Dioumaev, A B Rubin, D A Dolgikh, Valentin I. Gordeliy, J K Lanyi
    Abstract:

    This review covers the properties of a Retinal Protein (ESR) from the psychrotrophic bacterium Exiguobacterium sibiricum that functions as a light-driven proton pump. The presence of a lysine residue at the position corresponding to intramolecular proton donor for the Schiff base represents a unique structural feature of ESR. We have shown that Lys96 successfully facilitates delivery of protons from the cytoplasmic surface to the Schiff base, thus acting as a proton donor in ESR. Since proton uptake during the photocycle precedes Schiff base reprotonation, we conclude that this residue is initially in the uncharged state and acquires a proton for a short time after Schiff base deprotonation and M intermediate formation. Involvement of Lys as a proton donor distinguishes ESR from the related Retinal Proteins — bacteriorhodopsin (BR), proteorhodopsin (PR), and xanthorhodopsin (XR), in which the donor function is performed by residues with a carboxyl side chain. Like other eubacterial proton pumps (PR and XR), ESR contains a histidine residue interacting with the proton acceptor Asp85. In contrast to PR, this interaction leads to shift of the acceptor’s p K _a to more acidic pH, thus providing its ability to function over a wide pH range. The presence of a strong H-bond between Asp85 and His57, the structure of the proton-conducting pathways from cytoplasmic surface to the Schiff base and to extracellular surface, and other properties of ESR were demonstrated by solving its three-dimensional structure, which revealed several differences from known structures of BR and XR. The structure of ESR, its photocycle, and proton transfer reactions are discussed in comparison with homologous Retinal Proteins.

  • ESR - A Retinal Protein with Unusual Properties from Exiguobacterium sibiricum.
    Биохимия Biochemistry, 2015
    Co-Authors: L E Petrovskaya, S P Balashov, E P Lukashev, E S Imasheva, I Yu Gushchin, A K Dioumaev, A B Rubin, D A Dolgikh, Valentin I. Gordeliy, J K Lanyi
    Abstract:

    This review covers the properties of a Retinal Protein (ESR) from the psychrotrophic bacterium Exiguobacterium sibiricum that functions as a light-driven proton pump. The presence of a lysine residue at the position corresponding to intramolecular proton donor for the Schiff base represents a unique structural feature of ESR. We have shown that Lys96 successfully facilitates delivery of protons from the cytoplasmic surface to the Schiff base, thus acting as a proton donor in ESR. Since proton uptake during the photocycle precedes Schiff base reprotonation, we conclude that this residue is initially in the uncharged state and acquires a proton for a short time after Schiff base deprotonation and M intermediate formation. Involvement of Lys as a proton donor distinguishes ESR from the related Retinal Proteins - bacteriorhodopsin (BR), proteorhodopsin (PR), and xanthorhodopsin (XR), in which the donor function is performed by residues with a carboxyl side chain. Like other eubacterial proton pumps (PR and XR), ESR contains a histidine residue interacting with the proton acceptor Asp85. In contrast to PR, this interaction leads to shift of the acceptor's pKa to more acidic pH, thus providing its ability to function over a wide pH range. The presence of a strong H-bond between Asp85 and His57, the structure of the proton-conducting pathways from cytoplasmic surface to the Schiff base and to extracellular surface, and other properties of ESR were demonstrated by solving its three-dimensional structure, which revealed several differences from known structures of BR and XR. The structure of ESR, its photocycle, and proton transfer reactions are discussed in comparison with homologous Retinal Proteins.

  • Xanthorhodopsin: Proton pump with a carotenoid antenna
    Cellular and Molecular Life Sciences, 2007
    Co-Authors: S. P. Balashov, J K Lanyi
    Abstract:

    Retinal Proteins function as photoreceptors and ion pumps. Xanthorhodopsin of Salinibacter ruber is a recent addition to this diverse family. Its novel and distinctive feature is a second chromophore, a carotenoid, which serves as light-harvesting antenna. Here we discuss the properties of this carotenoid/Retinal complex most relevant to its function (such as the specific binding site controlled by the Retinal) and its relationship to other Retinal Proteins (bacteriorhodopsin, archaerhodopsin, proteorhodopsin and Retinal photoreceptors of archaea and eukaryotes). Antenna addition to a Retinal Protein has not been observed among the archaea and emerged in bacteria apparently in response to environmental conditions where light-harvesting becomes a limiting factor in Retinal Protein functioning.

  • Visions & Reflections (Minireview) Xanthorhodopsin: Proton pump with a carotenoid antenna
    2007
    Co-Authors: S. P. Balashov, J K Lanyi
    Abstract:

    Retinal Proteins function as photoreceptors and ion pumps. Xanthorhodopsin of Salinibacter ruber is a recent addition to this diverse family. Its novel and distinctive feature is a second chromophore, a caro- tenoid, which serves as light-harvesting antenna. Here we discuss the properties of this carotenoid/Retinal complex most relevant to its function (such as the specific binding site controlled by the Retinal) and its relationship to other Retinal Proteins (bacteriorho- dopsin, archaerhodopsin, proteorhodopsin and Retinal photoreceptors of archaea and eukaryotes). Antenna addition to a Retinal Protein has not been observed among the archaea and emerged in bacteria appa- rently in response to environmental conditions where light-harvesting becomes a limiting factor in Retinal Protein functioning.