AUSTRALIAN Halobacteria and THEIR RETINAL‐PROTEIN ION PUMPS*

Mukohata, Yasuo; Ihara, Kenji; Uegaki, Koichi; Mlyashita, Yukiya; Sugiyama, Yasuo

doi:10.1111/j.1751-1097.1991.tb02127.x

Cited by 46 publications

(54 citation statements)

References 29 publications

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“…3 A and B). These spectra closely matched corresponding spectra of Archaerhodopsin 1 (32) and BR (33). The pH-dependent transient absorption (Fig.…”

Section: Resultssupporting

confidence: 75%

Mechanism of voltage-sensitive fluorescence in a microbial rhodopsin

Maclaurin¹,

Venkatachalam

Lee

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

139

186

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Here, we present a detailed spectroscopic characterization of Archaerhodopsin 3 (Arch). We performed fluorescence spectroscopy on Arch and its photogenerated intermediates in Escherichia coli and in single HEK293 cells under voltage-clamp conditions. These experiments probed the effects of time-dependent illumination and membrane voltage on absorption, fluorescence, membrane current, and membrane capacitance. The fluorescence of Arch arises through a sequential three-photon process. Membrane voltage modulates protonation of the Schiff base in a 13-cis photocycle intermediate (M ⇌ N equilibrium), not in the ground state as previously hypothesized. We present experimental protocols for optimized voltage imaging with Arch, and we discuss strategies for engineering improved rhodopsin-based voltage indicators.

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“…3 A and B). These spectra closely matched corresponding spectra of Archaerhodopsin 1 (32) and BR (33). The pH-dependent transient absorption (Fig.…”

Section: Resultssupporting

confidence: 75%

Mechanism of voltage-sensitive fluorescence in a microbial rhodopsin

Maclaurin¹,

Venkatachalam

Lee

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

139

186

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“…Action spectra for bacteriorhodopsin ruled out an antenna function for bacterioruberin, the main carotenoid in halobacteria (13,27). No energy transfer was observed for archaerhodopsin either (28). We found that incubation of bacteriorhodopsin and proteorhodopsin with dodecyl maltoside-solubilized salinixanthin yielded no evidence for a complex (spectra not shown).…”

mentioning

confidence: 76%

Xanthorhodopsin: A Proton Pump with a Light-Harvesting Carotenoid Antenna

Balashov

Imasheva

Boichenko

et al. 2005

Science

323

395

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Energy transfer from antenna pigments to the reaction center is common in chlorophyll-based photosynthesis but never been observed in retinal-based ion pumps and photoreceptors. Here we describe xanthorhodopsin, a retinal protein/carotenoid complex in the eubacterium Salinibacter ruber, a proton pump. Difference absorption spectra measured under a variety of conditions and action spectra for pumping indicate that this protein contains two chromophores: retinal and the carotenoid, salinixanthin, in a molar ratio of about 1:1. The two chromophores strongly interact, and light energy absorbed by the carotenoid is efficiently transferred to the retinal and used for transmembrane proton transport.The extreme halophile Salinibacter ruber isolated from salt crystallizer ponds (1,2) can be grown in aerobic heterotrophic culture in 4 M NaCl. This eubacterium accumulates high concentrations of KCl to adapt to the high ionic strength (3), as the haloarchaea in the same environment. After several days of growth, Salinibacter ruber acquires a deep red color, from salinixanthin which constitutes nearly 100% of its carotenoid content and whose chemical structure was recently established (4). It was proposed to provide protection from photodamage and to stabilize the cell membrane because both the polyene and the fatty acid part of this carotenoid acyl glycoside will be immersed in the lipid bilayer (4). We report here that salinixanthin is not the only pigment in the Salinibacter ruber cell membrane, and heterotrophy is not the only source of energy for this organism. These cells contain an unusual retinal protein, which uses salinixanthin to assist harvesting light energy in a wider spectral range and utilizes it for transmembrane proton transport. Thus, it is a light-driven proton pump similar to bacteriorhodopsin (5) and the archaerhodopsins (6) of the archaea, the proteorhodopsins of planktobacteria (7), and leptosphaeria rhodopsin of an eukaryote (8), but with two chromophores. We term it here xanthorhodopsin. Its novel carotenoid antenna is a feature shared with chlorophyll-based light-harvesting complexes and reaction centers (9,10).Illumination of cell membrane vesicles prepared from Salinibacter produces acidification of the medium, which is abolished by the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) (Fig. 1A). When assayed in 1 M Na 2 SO 4 , these light-dependent pH changes are unaffected by the presence of chloride ions (not shown). Thus, the vesicles contain an outward-directed light-driven proton pump like bacteriorhodopsin, and lack a

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“…Aus-2 . The sequence identity among members of the archaerhodopsin family is high (>90%; Mukohata et al, 1991;Ihara et al, 1999), whereas the amino-acid sequences of all members of the aR family are distinct from those of protonpumping rhodopsins with known structure (i.e. the sequence identities are less than 50%).…”

Section: Introductionmentioning

confidence: 99%

Structure of archaerhodopsin-2 at 1.8 Å resolution

Kouyama

Fujii

Kanada

et al. 2014

Acta Crystallogr D Biol Crystallogr

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Archaerhodopsin-2 (aR2), the sole protein found in the claret membrane ofHalorubrumsp. Aus-2, functions as a light-driven proton pump. In this study, structural analysis of aR2 was performed using a novel three-dimensional crystal prepared by the successive fusion of claret membranes. The crystal is made up of stacked membranes, in each of which aR2 trimers are arranged on a hexagonal lattice. This lattice structure resembles that found in the purple membrane ofH. salinarum, except that lipid molecules trapped within the trimeric structure are not distributed with perfect threefold symmetry. Nonetheless, diffraction data at 1.8 Å resolution provide accurate structural information about functionally important residues. It is shown that two glutamates in the proton-release channel form a paired structure that is maintained by a low-barrier hydrogen bond. Although the structure of the proton-release pathway is highly conserved among proton-pumping archaeal rhodopsins, aR2 possesses the following peculiar structural features: (i) the motional freedom of the tryptophan residue that makes contact with the C13 methyl group of retinal is restricted, affecting the formation/decay kinetics of the L state, and (ii) the N-terminal polypeptide folds into an Ω-loop, which may play a role in organizing the higher-order structure.

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AUSTRALIAN Halobacteria and THEIR RETINAL‐PROTEIN ION PUMPS*

Cited by 46 publications

References 29 publications

Mechanism of voltage-sensitive fluorescence in a microbial rhodopsin

Mechanism of voltage-sensitive fluorescence in a microbial rhodopsin

Xanthorhodopsin: A Proton Pump with a Light-Harvesting Carotenoid Antenna

Structure of archaerhodopsin-2 at 1.8 Å resolution

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