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Clemens Glaubitz - One of the best experts on this subject based on the ideXlab platform.
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Proteorhodopsin photocycle kinetics between ph 5 and ph 9
Photochemistry and Photobiology, 2017Co-Authors: Thomas Kohler, Clemens Glaubitz, Ingrid Weber, Josef WachtveitlAbstract:The retinal protein Proteorhodopsin is a homolog of the well-characterized light-driven proton pump bacteriorhodopsin. Basic mechanisms of proton transport seem to be conserved, but there are noticeable differences in the pH ranges of proton transport. Proton transport and protonation state of a carboxylic acid side chain, the primary proton acceptor, are correlated. In case of Proteorhodopsin, the pKa of the primary proton acceptor Asp-97 (pKa ≈ 7.5) is unexpectedly close to environmental pH (pH ≈ 8). A significant fraction of Proteorhodopsin is possibly inactive at natural pH, in contrast to bacteriorhodopsin. We investigated photoinduced kinetics of Proteorhodopsin between pH 5 and pH 9 by time resolved UV/vis absorption spectroscopy. Kinetics is inhomogeneous within that pH region and can be considered as a superposition of two fractions. These fractions are correlated with the Asp-97 titration curve. Beside Asp-97, protonation equilibria of other groups influence kinetics, but the observations do not point toward major differences of primary proton acceptor function in Proteorhodopsin and bacteriorhodopsin. The pKa of Proteorhodopsin and some of its variants is suspected to be an example of molecular adaptation to the physiology of the original organisms.
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ultrafast photoinduced deactivation dynamics of Proteorhodopsin
Journal of Physical Chemistry Letters, 2017Co-Authors: Elias C Eckert, Clemens Glaubitz, Jagdeep Kaur, Josef WachtveitlAbstract:We report femtosecond time-resolved absorption change measurements of the photoinduced deactivation dynamics of a microbial rhodopsin in the ultraviolet–visible and mid-infrared range. The blue light quenching process is recorded in green Proteorhodopsin’s (GPR) primary proton donor mutant E108Q from the deprotonated 13-cis photointermediate. The return of GPR to the dark state occurs in two steps, starting with the photoinduced 13-cis to all-trans reisomerization of the retinal. The subsequent Schiff base reprotonation via the primary proton acceptor (D97) occurs on a nanosecond time scale. This step is two orders of magnitude faster than that in bacteriorhodopsin, potentially because of the very high pKA of the GPR primary proton acceptor.
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assembling a correctly folded and functional heptahelical membrane protein by protein trans splicing
Journal of Biological Chemistry, 2015Co-Authors: Michaela Mehler, Josef Wachtveitl, Carl Elias Eckert, Alena Busche, Jennifer Kulhei, Jonas Michaelis, Johanna Beckerbaldus, Volker Dotsch, Clemens GlaubitzAbstract:Protein trans-splicing using split inteins is well established as a useful tool for protein engineering. Here we show, for the first time, that this method can be applied to a membrane protein under native conditions. We provide compelling evidence that the heptahelical Proteorhodopsin can be assembled from two separate fragments consisting of helical bundles A and B and C, D, E, F, and G via a splicing site located in the BC loop. The procedure presented here is on the basis of dual expression and ligation in vivo. Global fold, stability, and photodynamics were analyzed in detergent by CD, stationary, as well as time-resolved optical spectroscopy. The fold within lipid bilayers has been probed by high field and dynamic nuclear polarization-enhanced solid-state NMR utilizing a (13)C-labeled retinal cofactor and extensively (13)C-(15)N-labeled protein. Our data show unambiguously that the ligation product is identical to its non-ligated counterpart. Furthermore, our data highlight the effects of BC loop modifications onto the photocycle kinetics of Proteorhodopsin. Our data demonstrate that a correctly folded and functionally intact protein can be produced in this artificial way. Our findings are of high relevance for a general understanding of the assembly of membrane proteins for elucidating intramolecular interactions, and they offer the possibility of developing novel labeling schemes for spectroscopic applications.
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fluorescence and excited state dynamics of the deprotonated schiff base retinal in Proteorhodopsin
Biological Chemistry, 2015Co-Authors: Elena Buhl, Clemens Glaubitz, Markus Braun, Andrea Lakatos, Josef WachtveitlAbstract:The UV light absorbing species of Proteorhodopsin with deprotonated Schiff base retinal was investigated using steady-state fluorescence and femtosecond pump-probe spectroscopy. Compared to the all-trans retinal with protonated Schiff base, the deprotonated chromophore absorbs at 365 nm and exhibits a blue-shifted fluorescence spectrum. The unusually long-lived excited state decays bi-exponentially with time constants of 8 ps and 130 ps to form a deprotonated 13-cis retinal as the primary photo-product.
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critical role of asp227 in the photocycle of Proteorhodopsin
Biochemistry, 2012Co-Authors: Julia Herz, Clemens Glaubitz, Ingrid Weber, Mirkakristin Verhoefen, Christian Bamann, Josef WachtveitlAbstract:The photocycle of the proton acceptor complex mutant D227N of the bacterial retinal protein Proteorhodopsin is investigated employing steady state pH-titration experiments in the UV-visible range as well as femtosecond-pump-probe spectroscopy and flash photolysis in the visible spectral range. The evaluation of the pH-dependent spectra showed that the neutralization of the charge at position 227 has a remarkable influence on the ground state properties of the protein. Both the pK(a) values of the primary proton acceptor and of the Schiff base are considerably decreased. Femtosecond-time-resolved measurements demonstrate that the general S(1) deactivation pathway; that is, the K-state formation is preserved in the D227N mutant. However, the pH-dependence of the reaction rate is lost by the substitution of Asp227 with an asparagine. Also no significant kinetic differences are observed upon deuteration. This is explained by the lack of a strongly hydrogen-bonded water in the vicinity of Asp97, Asp227, and the Schiff base or a change in the hydrogen bonding of it (Ikeda et al. (2007) Biochemistry 46, 5365-5373). The flash photolysis measurements prove a considerably elongated photocycle with pronounced pH-dependence. Interestingly, at pH 9 the M-state is visible until the end of the reaction cycle, leading to the conclusion that the mutation does not only lower the pK(a) of the Schiff base in the unphotolyzed ground state but also prevents an efficient reprotonation reaction.
Josef Wachtveitl - One of the best experts on this subject based on the ideXlab platform.
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Proteorhodopsin photocycle kinetics between ph 5 and ph 9
Photochemistry and Photobiology, 2017Co-Authors: Thomas Kohler, Clemens Glaubitz, Ingrid Weber, Josef WachtveitlAbstract:The retinal protein Proteorhodopsin is a homolog of the well-characterized light-driven proton pump bacteriorhodopsin. Basic mechanisms of proton transport seem to be conserved, but there are noticeable differences in the pH ranges of proton transport. Proton transport and protonation state of a carboxylic acid side chain, the primary proton acceptor, are correlated. In case of Proteorhodopsin, the pKa of the primary proton acceptor Asp-97 (pKa ≈ 7.5) is unexpectedly close to environmental pH (pH ≈ 8). A significant fraction of Proteorhodopsin is possibly inactive at natural pH, in contrast to bacteriorhodopsin. We investigated photoinduced kinetics of Proteorhodopsin between pH 5 and pH 9 by time resolved UV/vis absorption spectroscopy. Kinetics is inhomogeneous within that pH region and can be considered as a superposition of two fractions. These fractions are correlated with the Asp-97 titration curve. Beside Asp-97, protonation equilibria of other groups influence kinetics, but the observations do not point toward major differences of primary proton acceptor function in Proteorhodopsin and bacteriorhodopsin. The pKa of Proteorhodopsin and some of its variants is suspected to be an example of molecular adaptation to the physiology of the original organisms.
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ultrafast photoinduced deactivation dynamics of Proteorhodopsin
Journal of Physical Chemistry Letters, 2017Co-Authors: Elias C Eckert, Clemens Glaubitz, Jagdeep Kaur, Josef WachtveitlAbstract:We report femtosecond time-resolved absorption change measurements of the photoinduced deactivation dynamics of a microbial rhodopsin in the ultraviolet–visible and mid-infrared range. The blue light quenching process is recorded in green Proteorhodopsin’s (GPR) primary proton donor mutant E108Q from the deprotonated 13-cis photointermediate. The return of GPR to the dark state occurs in two steps, starting with the photoinduced 13-cis to all-trans reisomerization of the retinal. The subsequent Schiff base reprotonation via the primary proton acceptor (D97) occurs on a nanosecond time scale. This step is two orders of magnitude faster than that in bacteriorhodopsin, potentially because of the very high pKA of the GPR primary proton acceptor.
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assembling a correctly folded and functional heptahelical membrane protein by protein trans splicing
Journal of Biological Chemistry, 2015Co-Authors: Michaela Mehler, Josef Wachtveitl, Carl Elias Eckert, Alena Busche, Jennifer Kulhei, Jonas Michaelis, Johanna Beckerbaldus, Volker Dotsch, Clemens GlaubitzAbstract:Protein trans-splicing using split inteins is well established as a useful tool for protein engineering. Here we show, for the first time, that this method can be applied to a membrane protein under native conditions. We provide compelling evidence that the heptahelical Proteorhodopsin can be assembled from two separate fragments consisting of helical bundles A and B and C, D, E, F, and G via a splicing site located in the BC loop. The procedure presented here is on the basis of dual expression and ligation in vivo. Global fold, stability, and photodynamics were analyzed in detergent by CD, stationary, as well as time-resolved optical spectroscopy. The fold within lipid bilayers has been probed by high field and dynamic nuclear polarization-enhanced solid-state NMR utilizing a (13)C-labeled retinal cofactor and extensively (13)C-(15)N-labeled protein. Our data show unambiguously that the ligation product is identical to its non-ligated counterpart. Furthermore, our data highlight the effects of BC loop modifications onto the photocycle kinetics of Proteorhodopsin. Our data demonstrate that a correctly folded and functionally intact protein can be produced in this artificial way. Our findings are of high relevance for a general understanding of the assembly of membrane proteins for elucidating intramolecular interactions, and they offer the possibility of developing novel labeling schemes for spectroscopic applications.
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fluorescence and excited state dynamics of the deprotonated schiff base retinal in Proteorhodopsin
Biological Chemistry, 2015Co-Authors: Elena Buhl, Clemens Glaubitz, Markus Braun, Andrea Lakatos, Josef WachtveitlAbstract:The UV light absorbing species of Proteorhodopsin with deprotonated Schiff base retinal was investigated using steady-state fluorescence and femtosecond pump-probe spectroscopy. Compared to the all-trans retinal with protonated Schiff base, the deprotonated chromophore absorbs at 365 nm and exhibits a blue-shifted fluorescence spectrum. The unusually long-lived excited state decays bi-exponentially with time constants of 8 ps and 130 ps to form a deprotonated 13-cis retinal as the primary photo-product.
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the ef loop in green Proteorhodopsin affects conformation and photocycle dynamics
Biophysical Journal, 2013Co-Authors: Michaela Mehler, Markus Braun, Johanna Beckerbaldus, Frank Scholz, Sandra J Ullrich, Jiafei Mao, Lynda J Brown, Richard C D Brown, Sarah A Fiedler, Josef WachtveitlAbstract:The Proteorhodopsin family consists of retinal proteins of marine bacterial origin with optical properties adjusted to their local environments. For green Proteorhodopsin, a highly specific mutation in the EF loop, A178R, has been found to cause a surprisingly large redshift of 20 nm despite its distance from the chromophore. Here, we analyze structural and functional consequences of this EF loop mutation by time-resolved optical spectroscopy and solid-state NMR. We found that the primary photoreaction and the formation of the K-like photo intermediate is almost pH-independent and slower compared to the wild-type, whereas the decay of the K-intermediate is accelerated, suggesting structural changes within the counterion complex upon mutation. The photocycle is significantly elongated mainly due to an enlarged lifetime of late photo intermediates. Multidimensional MAS-NMR reveals mutation-induced chemical shift changes propagating from the EF loop to the chromophore binding pocket, whereas dynamic nuclear polarization-enhanced 13C-double quantum MAS-NMR has been used to probe directly the retinylidene conformation. Our data show a modified interaction network between chromophore, Schiff base, and counterion complex explaining the altered optical and kinetic properties. In particular, the mutation-induced distorted structure in the EF loop weakens interactions, which help reorienting helix F during the reprotonation step explaining the slower photocycle. These data lead to the conclusion that the EF loop plays an important role in proton uptake from the cytoplasm but our data also reveal a clear interaction pathway between the EF loop and retinal binding pocket, which might be an evolutionary conserved communication pathway in retinal proteins.
Klaas J Hellingwerf - One of the best experts on this subject based on the ideXlab platform.
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combining retinal based and chlorophyll based oxygenic photosynthesis Proteorhodopsin expression increases growth rate and fitness of a psi strain of synechocystis sp pcc6803
Metabolic Engineering, 2019Co-Authors: Que Chen, Srividya Ganapathy, Jos C Arents, Merijn J Schuurmans, Willem J De Grip, Otilia Cheregi, Christiane Funk, Filipe Branco Dos Santos, Klaas J HellingwerfAbstract:To fill the "green absorption gap", a green absorbing Proteorhodopsin was expressed in a PSI-deletion strain (Delta PSI) of Synechocystis sp. PCC6803. Growth-rate measurements, competition experime ...
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expression of holo Proteorhodopsin in synechocystis sp pcc 6803
Metabolic Engineering, 2016Co-Authors: Que Chen, W.j. De ,grip, Srividya Ganapathy, J B Van Der Steen, Henk L Dekker, Klaas J HellingwerfAbstract:Retinal-based photosynthesis may contribute to the free energy conversion needed for growth of an organism carrying out oxygenic photosynthesis, like a cyanobacterium. After optimization, this may even enhance the overall efficiency of phototrophic growth of such organisms in sustainability applications. As a first step towards this, we here report on functional expression of the archetype Proteorhodopsin in Synechocystis sp. PCC 6803. Upon use of the moderate-strength psbA2 promoter, holo-Proteorhodopsin is expressed in this cyanobacterium, at a level of up to 10(5) molecules per cell, presumably in a hexameric quaternary structure, and with approximately equal distribution (on a protein-content basis) over the thylakoid and the cytoplasmic membrane fraction. These results also demonstrate that Synechocystis sp. PCC 6803 has the capacity to synthesize all-trans-retinal. Expressing a substantial amount of a heterologous opsin membrane protein causes a substantial growth retardation Synechocystis, as is clear from a strain expressing PROPS, a non-pumping mutant derivative of Proteorhodopsin. Relative to this latter strain, Proteorhodopsin expression, however, measurably stimulates its growth.
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characterization of the primary photochemistry of Proteorhodopsin with femtosecond spectroscopy
Biophysical Journal, 2008Co-Authors: Alisa Rupenyan, Klaas J Hellingwerf, Jos C Arents, Ivo H M Van Stokkum, Rienk Van Grondelle, Marie Louise GrootAbstract:Proteorhodopsin is an ion-translocating member of the microbial rhodopsin family. Light absorption by its retinal chromophore initiates a photocycle, driven by trans/cis isomerization, leading to transmembrane translocation of a proton toward the extracellular side of the cytoplasmic membrane. Here we report a study on the photoisomerization dynamics of the retinal chromophore of Proteorhodopsin, using femtosecond time-resolved spectroscopy, by probing in the visible- and in the midinfrared spectral regions. Experiments were performed both at pH 9.5 (a physiologically relevant pH value in which the primary proton acceptor of the protonated Schiff base, Asp97, is deprotonated) and at pH 6.5 (with Asp97 protonated). Simultaneous analysis of the data sets recorded in the two spectral regions and at both pH values reveals a multiexponential excited state decay, with time constants of ∼0.2 ps, ∼2 ps, and ∼20 ps. From the difference spectra associated with these dynamics, we conclude that there are two chromophore-isomerizaton pathways that lead to the K-state: one with an effective rate of ∼(2 ps)−1 and the other with a rate of ∼(20 ps)−1. At high pH, both pathways are equally effective, with an estimated quantum yield for K-formation of ∼0.7. At pH 6.5, the slower pathway is less productive, which results in an isomerization quantum yield of 0.5. We further observe an ultrafast response of residue Asp227, which forms part of the counterion complex, corresponding to a strengthening of its hydrogen bond with the Schiff base on K-state formation; and a feature that develops on the 0.2 ps and 2 ps timescale and probably reflects a response of an amide II band in reaction to the isomerization process.
Janos K Lanyi - One of the best experts on this subject based on the ideXlab platform.
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formation of a long lived photoproduct with a deprotonated schiff base in Proteorhodopsin and its enhancement by mutation of asp227
Biochemistry, 2005Co-Authors: Eleonora S Imasheva, Kazumi Shimono, Sergei P Balashov, Jennifer M Wang, Uri Zadok, Mordechai Sheves, Naoki Kamo, Janos K LanyiAbstract:Proteorhodopsin, a retinal protein of marine proteobacteria similar to bacteriorhodopsin of the archaea, is a light-driven proton pump. Absorption of a light quantum initiates a reaction cycle (tur...
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proton transport by Proteorhodopsin requires that the retinal schiff base counterion asp 97 be anionic
Biochemistry, 2003Co-Authors: Andrei K Dioumaev, Gyorgy Varo, Jennifer M Wang, Zoltan Balint, Janos K LanyiAbstract:At pH >7, Proteorhodopsin functions as an outward-directed proton pump in cell membranes, and Asp-97 and Glu-108, the homologues of the Asp-85 and Asp-96 in bacteriorhodopsin, are the proton acceptor and donor to the retinal Schiff base, respectively. It was reported, however [Friedrich, T. et al. (2002) J. Mol. Biol., 321, 821−838], that Proteorhodopsin transports protons also at pH <7 where Asp-97 is protonated and in the direction reverse from that at higher pH. To explore the roles of Asp-97 and Glu-108 in the proposed pumping with variable vectoriality, we compared the photocycles of D97N and E108Q mutants, and the effects of azide on the photocycle of the E108Q mutant, at low and high pH. Unlike at high pH, at a pH low enough to protonate Asp-97 neither the mutations nor the effects of azide revealed evidence for the participation of the acidic residues in proton transfer, and as in the photocycle of the wild-type protein, no intermediate with unprotonated Schiff base accumulated. In view of these f...
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the photochemical reaction cycle of Proteorhodopsin at low ph
Biophysical Journal, 2003Co-Authors: Melinda Lakatos, Janos K Lanyi, Julianna Szakacs, Gyorgy VaroAbstract:The proton acceptor group in the recently described retinal protein, Proteorhodopsin has an unusually high pKa of 7.1. It was shown that at pH above this pKa, illumination initiates a photocycle similar to that of bacteriorhodopsin, and the protein transports proton across the cell membrane. Recently it was reported that Proteorhodopsin, unlike bacteriorhodopsin, transports protons at pH below the pKa of the proton acceptor, and this transport is in the reverse direction. We have investigated the photocycle of Proteorhodopsin at such low pH. At pH 5, three spectrally distinct intermediates K, L, and N, and another spectrally silent one, PR′, could be identified, but a deprotonated Schiff base containing M-like intermediate, characteristic for proton pumping activity, does not accumulate. All the reactions between the intermediates are close to equilibrium, except the last transition from PR′ to PR, when the protein returns to its initial unexcited state in a quasiunidirectional reaction. The electric signal measurements indicate that although charge motions are detected inside the protein, their net dislocation is zero, indicating that contrary to the earlier reported, at low pH no charged particle is transported across the membrane.
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Characterization of the photochemical reaction cycle of Proteorhodopsin
Biophysical Journal, 2003Co-Authors: Gyorgy Varo, Melinda Lakatos, Leonid S. Brown, Janos K LanyiAbstract:Absorption changes in the photocycle of the recently described retinal protein, Proteorhodopsin, are analyzed. The transient spectra at pH 9.5, where it acts as a light-driven proton pump, reveal the existence of three spectrally different intermediates, K, M, and N, named in analogy with the photointermediates of bacteriorhodopsin. Model analysis based on time-dependent absorption kinetic signals at four wavelengths suggested the existence of two more spectrally silent intermediates and lead to a sequential reaction scheme with five intermediates, K, M1, M2, N, and PR′, before decay to the initial state PR. An L-like intermediate was not observed, probably for kinetic reasons. By measuring the light-generated electric signal of an oriented sample, the electrogenicity of each intermediate could be determined. The electrogenicities of the first three intermediates (K, M1, and M2) have small negative value, but the last three components, corresponding to the N and PR′ intermediates and PR, are positive and two-orders-of-magnitude larger. These states give the major contributions to the proton translocation across the membrane. The energetic scheme of the photocycle was calculated from the temperature-dependence of the absorption kinetic signals.
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proton transfers in the photochemical reaction cycle of Proteorhodopsin
Biochemistry, 2002Co-Authors: Andrei K Dioumaev, Leonid S. Brown, John L. Spudich, Elena N. Spudich, Jennifer Shih, Janos K LanyiAbstract:The spectral and photochemical properties of Proteorhodopsin (PR) were determined to compare its proton transport steps to those of bacteriorhodopsin (BR). Static and time-resolved measurements on wild-type PR and several mutants were done in the visible and infrared (FTIR and FT-Raman). Assignment of the observed CO stretch bands indicated that Asp-97 and Glu-108 serve as the proton acceptor and donor, respectively, to the retinal Schiff base, as do the residues at corresponding positions in BR, but there are numerous spectral and kinetic differences between the two proteins. There is no detectable dark-adaptation in PR, and the chromophore contains nearly entirely all-trans retinal. Because the pKa of Asp-97 is relatively high (7.1), the proton-transporting photocycle is produced only at alkaline pH. It contains at least seven transient states with decay times in the range from 10 μs to 200 ms, but the analysis reveals only three distinct spectral forms. The first is a red-shifted K-like state. Proton r...
Jarone Pinhassi - One of the best experts on this subject based on the ideXlab platform.
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marine bacterial and archaeal ion pumping rhodopsins genetic diversity physiology and ecology
Microbiology and Molecular Biology Reviews, 2016Co-Authors: Jarone Pinhassi, Edward F. Delong, Jose M Gonzalez, Oded Béjà, Carlos PedrosalioAbstract:The recognition of a new family of rhodopsins in marine planktonic bacteria, proton-pumping Proteorhodopsin, expanded the known phylogenetic range, environmental distribution, and sequence diversit ...
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stimulation of growth by Proteorhodopsin phototrophy involves regulation of central metabolic pathways in marine planktonic bacteria
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Joakim Palovaara, Jose M Gonzalez, Carlos Pedrosalio, Neelam Akram, Jeremy Forsberg, Federico Baltar, Carina Bunse, Jarone PinhassiAbstract:Proteorhodopsin (PR) is present in half of surface ocean bacterioplankton, where its light-driven proton pumping provides energy to cells. Indeed, PR promotes growth or survival in different bacter ...
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regulation of Proteorhodopsin gene expression by nutrient limitation in the marine bacterium vibrio sp and4
Environmental Microbiology, 2013Co-Authors: Neelam Akram, Jose M Gonzalez, Debra L. Milton, Joakim Palovaara, Jeremy Forsberg, Markus V Lindh, Haiwei Luo, Jarone PinhassiAbstract:Proteorhodopsin (PR), a ubiquitous membrane photoprotein in marine environments, acts as a light-driven proton pump and can provide energy for bacterial cellular metabolism. However, knowledge of f ...
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Genomics of the Proteorhodopsin-Containing Marine Flavobacterium Dokdonia sp. Strain MED134†
Applied and environmental microbiology, 2011Co-Authors: Jose M Gonzalez, Jarone Pinhassi, Laura Gómez-consarnau, Montserrat Coll-lladó, Beatriz Fernandez-gomez, Mónica González-velázquez, Pere Puigbò, Sebastian Jaenicke, Antoni Fernández-guerra, Alexander GoesmannAbstract:Proteorhodopsin phototrophy is expected to have considerable impact on the ecology and biogeochemical roles of marine bacteria. However, the genetic features contributing to the success of Proteorhodopsin-containing bacteria remain largely unknown. We investigated the genome of Dokdonia sp. strain MED134 (Bacteroidetes) for features potentially explaining its ability to grow better in light than darkness. MED134 has a relatively high number of peptidases, suggesting that amino acids are the main carbon and nitrogen sources. In addition, MED134 shares with other environmental genomes a reduction in gene copies at the expense of important ones, like membrane transporters, which might be compensated by the presence of the Proteorhodopsin gene. The genome analyses suggest Dokdonia sp. MED134 is able to respond to light at least partly due to the presence of a strong flavobacterial consensus promoter sequence for the Proteorhodopsin gene. Moreover, Dokdonia sp. MED134 has a complete set of anaplerotic enzymes likely to play a role in the adaptation of the carbon anabolism to the different sources of energy it can use, including light or various organic matter compounds. In addition to promoting growth, Proteorhodopsin phototrophy could provide energy for the degradation of complex or recalcitrant organic matter, survival during periods of low nutrients, or uptake of amino acids and peptides at low concentrations. Our analysis suggests that the ability to harness light potentially makes MED134 less dependent on the amount and quality of organic matter or other nutrients. The genomic features reported here may well be among the keys to a successful photoheterotrophic lifestyle.
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Proteorhodopsin phototrophy promotes survival of marine bacteria during starvation.
PLoS biology, 2010Co-Authors: Laura Gómez-consarnau, Jose M Gonzalez, Neelam Akram, Kristoffer Lindell, Anders Pedersen, Richard Neutze, Debra L. Milton, Jarone PinhassiAbstract:Proteorhodopsins are globally abundant photoproteins found in bacteria in the photic zone of the ocean. Although their function as proton pumps with energy-yielding potential has been demonstrated, the ecological role of Proteorhodopsins remains largely unexplored. Here, we report the presence and function of Proteorhodopsin in a member of the widespread genus Vibrio, uncovered through whole-genome analysis. Phylogenetic analysis suggests that the Vibrio strain AND4 obtained Proteorhodopsin through lateral gene transfer, which could have modified the ecology of this marine bacterium. We demonstrate an increased long-term survival of AND4 when starved in seawater exposed to light rather than held in darkness. Furthermore, mutational analysis provides the first direct evidence, to our knowledge, linking the Proteorhodopsin gene and its biological function in marine bacteria. Thus, Proteorhodopsin phototrophy confers a fitness advantage to marine bacteria, representing a novel mechanism for bacterioplankton to endure frequent periods of resource deprivation at the ocean's surface.
