The Photophobic Receptor from Natronobacterium pharaonis: Temperature and pH Dependencies of the Photocycle of Sensory Rhodopsin II

Chizhov, Igor; Schmies, Georg; Seidel, R.; Sydor, Jens; Lüttenberg, Beate; Engelhard, Martin

doi:10.1016/s0006-3495(98)77588-5

Cited by 171 publications

(274 citation statements)

References 45 publications

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“…In this time window all peaks exhibit a gradual decrease in intensity reflecting the return of complex to the unphotolyzed state. The majority of peaks including the negative retinal vibrational modes at 1200, 1240, and 1545 cm Ϫ1 and the carboxylic stretching mode at 1764 cm Ϫ1 exhibit an exponential decay (data not shown) with a time decay constant similar to that previously reported (38). Because there is no noticeable delay between the decay of these receptor vibrations and the 1694 cm Ϫ1 band assigned to Asn 74 from the transducer, we conclude that the recovery of the Tyr 199 -Asn 74 hydrogen bonding occurs at a similar rate as SRII returns to the unphotolyzed state.…”

supporting

confidence: 81%

Photoactivation Perturbs the Membrane-embedded Contacts between Sensory Rhodopsin II and Its Transducer

Bergo

Spudich

Rothschild

et al. 2005

Journal of Biological Chemistry

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The photoactivation mechanism of the sensory rhodopsin II (SRII)-HtrII receptor-transducer complex of Natronomonas pharaonis was investigated by time-resolved Fourier transform infrared difference spectroscopy to identify structural changes associated with early events in the signal relay mechanism from the receptor to the transducer. Several prominent bands in the wild-type SRII-HtrII spectra are affected by amino acid substitutions at the receptor Sensory rhodopsin II (SRII)1 functions as a phototaxis receptor for blue light avoidance in several halophilic archaea (1-4). This protein belongs to a growing family of microbial rhodopsins, seven-helix retinylidene membrane proteins now found in all domains of life (5-8). The SRII receptor forms a tight intermolecular complex with its cognate transducer protein HtrII in the cell membrane. The transducer, like its homologous methyl-accepting chemotaxis transducers, possesses two transmembrane helices and a large cytoplasmic domain that binds at its distal end a His-kinase that phosphorylates a flagellar motor switch regulator (1, 9).Interactions of HtrII with the SRII receptor are localized to the transducer transmembrane and membrane-proximal domains (10, 11). A crystal structure of SRII bound to an Nterminal HtrII fragment containing the transmembrane helices (TM1 and TM2) shows tight van der Waals interaction and three hydrogen bonds between TM2 and SRII helices F and G (12). An atomic structure of the membrane-proximal domain of the transducer is not available; however, fluorescent probe accessibility and Förster resonance energy transfer measurements show interaction of this domain with the cytoplasmic E-F loop of the receptor (13).The signal relay mechanism from SRII to HtrII in the complex has become a focus of interest in the past several years, in part because of its importance to the general understanding of interaction between integral membrane proteins. In accord with the unified model for transport and signaling by microbial rhodopsins (14, 15), the key event in the transducer activation is an outward tilt of the receptor helix F during the lifetime of its M intermediate, which has been directly detected by EPR of paramagnetic probes in the free receptor (16) and in its complex with transducer (17). In a response to the helix F movements, the TM2 of HtrII is displaced from its initial position (17). Additional structural changes were observed in the cytoplasmic membrane proximal region by fluorescent probe accessibility measurements (13).Fourier transform infrared (FTIR) difference spectroscopy has been used extensively in the past to elucidate structural changes in the photocycles of several microbial rhodopsins (18 -27). This technique measures changes in the infrared absorption of protein groups and enables studies of light-induced conformational changes without the necessity of introducing potentially structure-perturbing probes. Because of its sensitivity to small changes in hydrogen bonding, it is especially well suited for the study of interacti...

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supporting

confidence: 81%

Photoactivation Perturbs the Membrane-embedded Contacts between Sensory Rhodopsin II and Its Transducer

Bergo

Spudich

Rothschild

et al. 2005

Journal of Biological Chemistry

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“…The long-lasting absorption changes (ϱ-component) demonstrate the existence of a redshifted photoproduct in the 100-ps to the nanosecond range. This state can be identified as a K-like intermediate found in flash photolysis measurements (29,35,36). The similar decayassociated spectra of the infinite and the 5-ps kinetic components indicate a species with a stronger red shift-we call it SRII J-populated for 5 ps.…”

Section: Discussionmentioning

confidence: 61%

Primary reactions of sensory rhodopsins

Lutz¹

2001

Proceedings of the National Academy of Sciences

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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 pump͞probe spectroscopy and steady-state fluorescence spectroscopy. The data for both species of the bluelight 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.S ensory rhodopsin (SR) I and II are members of the family of retinal-containing membrane proteins of archaea, which also includes the well-known ion pumps bacteriorhodopsin (BR) and halorhodopsin (HR). SRI and SRII act as receptors in phototaxis. In this process light absorption triggers movement of the flagellated cells toward favorable or away from unfavorable environments, depending on the wavelength of the absorbed light. Thus, the SRs provide a simple color-sensing mechanism (1) for haloarchaea like Halobacterium salinarum and other species. Attractant and repellent reactions of the cell are triggered by light absorption of specific photochromic states of these photoreceptors. In SRI, the dark-adapted state SRI 587 is converted into a blue-shifted intermediate S 373 by absorbing orange light around 590 nm (2), leading to positive signaling via the closely coupled transducer protein HtrI (3). Absorption of a UV photon in the S 373 state leads to a repellent stimulus, resulting in a photophobic response of the cell. SRII is a blue-light receptor with maximum ground-state absorption around 490 nm. The repellent signaling is initiated by the intermediate SRII 360 (M) in the course of the SRII photocycle (4).SRI and SRII are structurally very similar to BR and HR; sequence homology is especially striking in the chromophore environment (5, 6). Although 13 of 21 residues in a 5-Å shell around the retinal atoms are strictly conserved in BR, HR, and SRI of all species sequenced to date, SRII has three residues less conserved (7). This might be one reason for the blue-shifted absorption maximum of SRII compared with the other archaeal receptor proteins (8). Photoexcitation triggers a series of conformational changes initiated by trans-cis isomerization of the retinal chromophore in all retinal-containing membrane proteins (9). The first events lead to the formation of a red-shifted intermediate observed on the subnanosecond ...

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“…4, lower panel) result in a higher level of O intermediate, which gradually appears during the late photocycle for both SRII and the SRII-HtrII complex. This alteration is not surprising because D 2 O is known to alter the kinetics of SRII (13). However, most of the features that distinguish the receptor and the fusion complex are still present, including the increase intensity in the region near 1690 cm Ϫ1 , reduction in the negative band at 1664 cm Ϫ1 , and the appearance of a pronounced shoulder near 1555 cm Ϫ1 .…”

Section: Comparison Of Late Photocycles Of Receptor and Fusion Complexmentioning

confidence: 97%

Conformational Changes Detected in a Sensory Rhodopsin II-Transducer Complex

Bergo

Spudich

et al. 2003

Journal of Biological Chemistry

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Sensory rhodopsins (SRs) are light receptors that belong to the growing family of microbial rhodopsins. SRs have now been found in all three major domains of life including archaea, bacteria, and eukaryotes. One of the most extensively studied sensory rhodopsins is SRII, which controls a blue light avoidance motility response in the halophilic archaeon Natronobacterium pharaonis. This seven-helix integral membrane protein forms a tight intermolecular complex with its cognate transducer protein, HtrII. In this work, the structural changes occurring in a fusion complex consisting of SRII and the two transmembrane helices (TM1 and TM2) of HtrII were investigated by time-resolved Fourier transform infrared difference spectroscopy. Although most of the structural changes observed in SRII are conserved in the fusion complex, several distinct changes are found. A reduction in the intensity of a prominent amide I band observed for SRII indicates that its structural changes are altered in the fusion complex, possibly because of the close interaction of TM2 with the F helix, which interferes with the F helix outward tilt. Deprotonation of at least one Asp/Glu residue is detected in the transducer-free receptor with a pK a near 7 that is abolished or altered in the fusion complex. Changes are also detected in spectral regions characteristic of Asn and Tyr vibrations. At high hydration levels, transducer-fusion interactions lead to a stabilization of an M-like intermediate that most likely corresponds to an active signaling form of the transducer. These findings are discussed in the context of a recently elucidated x-ray structure of the fusion complex. Sensory rhodopsin (SR)1 II is a seven-helix integral membrane protein found in halophilic archaea that functions as a light receptor for negative phototaxis (1). Together with sensory rhodopsin I (SRI), which is a dual photoattractant/photorepellent receptor (2); bacteriorhodopsin (BR), a light-driven proton pump; and halorhodopsin, a light-driven chloride pump, these proteins belong to a widespread family of photoactive retinylidene proteins or microbial rhodopsins (3). Microbial rhodopsins have several common features including an alltrans-retinylidene chromophore covalently attached to the protein via a protonated Schiff base linkage. Light absorption results in an all-trans 3 13-cis-isomerization of the chromophore that triggers subsequent conformational changes associated with a photocycle characteristic of each protein. Members of the microbial rhodopsin family have recently been found in diverse organisms including marine proteobacteria (4), cyanobacteria (5), and lower eukaryotes such as Neurospora crassa (6) and Chlamydomonas reinhardtii (7).Sensory rhodopsin II transmits the photorepellent signal to the cell cytoplasm by activating the transmembrane domain of its cognate transducer HtrII (8), 2 which is tightly bound to the receptor helices F and G (9). The photocycle of SRII comprises several photointermediates (10 -13), including the blue-shifted M and red-shifte...

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The Photophobic Receptor from Natronobacterium pharaonis: Temperature and pH Dependencies of the Photocycle of Sensory Rhodopsin II

Cited by 171 publications

References 45 publications

Photoactivation Perturbs the Membrane-embedded Contacts between Sensory Rhodopsin II and Its Transducer

Photoactivation Perturbs the Membrane-embedded Contacts between Sensory Rhodopsin II and Its Transducer

Primary reactions of sensory rhodopsins

Conformational Changes Detected in a Sensory Rhodopsin II-Transducer Complex

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