Steric Constraint in the Primary Photoproduct of an Archaeal Rhodopsin from Regiospecific Perturbation of C−D Stretching Vibration of the Retinyl Chromophore

Sudo, Yuki; Furutani, Yuji; Wada, Akimori; Ito, Masayoshi; Kamo, Naoki; Kandori, Hideki

doi:10.1021/ja056203a

Cited by 41 publications

(85 citation statements)

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“…40). This destabilizing bond energization likely results from a local steric constraint between the retinal C 14 -H and Thr-204, caused by C 13 AC 14 double-bond rotation (41). The HtrII dependence of this reaction indicates that the bonded Tyr-Thr pair is coupled to the receptor-transducer interface, where chemical signal relay occurs.…”

Section: Resultsmentioning

confidence: 98%

Three strategically placed hydrogen-bonding residues convert a proton pump into a sensory receptor

Sudo

Spudich

2006

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

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In haloarchaea, light-driven ion transporters have been modified by evolution to produce sensory receptors that relay light signals to transducer proteins controlling motility behavior. The proton pump bacteriorhodopsin and the phototaxis receptor sensory rhodopsin II (SRII) differ by 74% of their residues, with nearly all conserved residues within the photoreactive retinal-binding pocket in the membrane-embedded center of the proteins. Here, we show that three residues in bacteriorhodopsin replaced by the corresponding residues in SRII enable bacteriorhodopsin to efficiently relay the retinal photoisomerization signal to the SRII integral membrane transducer (HtrII) and induce robust phototaxis responses. A single replacement (Ala-215-Thr), bridging the retinal and the membrane-embedded surface, confers weak phototaxis signaling activity, and the additional two (surface substitutions Pro-200 -Thr and Val-210 -Tyr), expected to align bacteriorhodopsin and HtrII in similar juxtaposition as SRII and HtrII, greatly enhance the signaling. In SRII, the three residues form a chain of hydrogen bonds from the retinal's photoisomerized C13AC14 double bond to residues in the membrane-embedded ␣-helices of HtrII. The results suggest a chemical mechanism for signaling that entails initial storage of energy of photoisomerization in SRII's hydrogen bond between Tyr-174, which is in contact with the retinal, and Thr-204, which borders residues on the SRII surface in contact with HtrII, followed by transfer of this chemical energy to drive structural transitions in the transducer helices. The results demonstrate that evolution accomplished an elegant but simple conversion: The essential differences between transport and signaling proteins in the rhodopsin family are far less than previously imagined.bacteriorhodopsin ͉ phototaxis ͉ retinal ͉ sensory rhodopsin ͉ transport M icrobial rhodopsins are photochemically reactive membrane-embedded proteins with seven transmembrane ␣-helices that form a pocket for the chromophore retinal. They are widespread in the microbial world in prokaryotes (bacteria and archaea) and in eukaryotes (fungi and algae) (1-3). A striking characteristic of these photoactive proteins is their wide range of seemingly dissimilar functions. Some are light-driven transporters, such as the proton pumps bacteriorhodopsin (BR) in haloarchaea (4) and proteorhodopsin in marine bacteria (5). Others are light sensors, such as the phototaxis receptors sensory rhodopsins (SR) I and II in haloarchaea (6-8). These sensory rhodopsins relay signals by protein-protein interaction to SR integral membrane transducer proteins (Htr) I and II, respectively. The signal relay mechanism from SR receptors to their cognate Htr transducers has become a focus of interest in part because of its importance to the general understanding of communication between integral membrane proteins, about which little is known.A close relationship between transport and sensory signaling activities was revealed when SRI was separated from its tight co...

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Section: Resultsmentioning

confidence: 98%

Three strategically placed hydrogen-bonding residues convert a proton pump into a sensory receptor

Sudo

Spudich

2006

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

Self Cite

102

125

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“…What (43). It is likely that Thr 204 is the counterpart of the C 14 -D group, and enhanced absorption probably originates from the local steric constraint at the C 14 -D position after the C 13 ϭC 14 double bond rotation.…”

Section: Discussionmentioning

confidence: 99%

Functional Importance of the Interhelical Hydrogen Bond between Thr204 and Tyr174 of Sensory Rhodopsin II and Its Alteration during the Signaling Process

Sudo

Furutani

Kandori

et al. 2006

Journal of Biological Chemistry

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Sensory rhodopsin II (SRII), a receptor for negative phototaxis in haloarchaea, transmits light signals through changes in protein-protein interaction with its transducer HtrII. Light-induced structural changes throughout the SRII-HtrII interface, which spans the periplasmic region, membrane-embedded domains, and cytoplasmic domains near the membrane, have been identified by several studies. Here we demonstrate by sitespecific mutagenesis and analysis of phototaxis behavior that two residues in SRII near the membrane-embedded interface (Tyr 174 on helix F and Thr 204 on helix G) are essential for signaling by the SRII-HtrII complex. These residues, which are the first in SRII shown to be required for phototaxis function, provide biological significance to the previous observation that the hydrogen bond between them is strengthened upon the formation of the earliest SRII photointermediate (SRII K ) only when SRII is complexed with HtrII. Here we report frequency changes of the S-H stretch of a cysteine substituted for SRII Thr 204 in the signaling state intermediates of the SRII photocycle, as well as an influence of HtrII on the hydrogen bond strength, supporting a direct role of the hydrogen bond in SRII-HtrII signal relay chemistry. Our results suggest that the light signal is transmitted to HtrII from the energized interhelical hydrogen bond between Thr 204 and Tyr 174 , which is located at both the retinal chromophore pocket and in helices F and G that form the membrane-embedded interaction surface to the signal-bearing second transmembrane helix of HtrII. The results argue for a critical process in signal relay occurring at this membrane interfacial region of the complex. Sensory rhodopsin II (SRII,2 also known as phoborhodopsin) is a negative phototaxis receptor in haloarchaeal prokaryotes, including Halobacterium salinarum and Natronomonas pharaonis (1-5). The SRII photoreceptor subunit forms a 2:2 complex with its transducer subunit, HtrII, in membranes and transmits light signals through changes in protein-protein interaction. The photochemical reaction cycle (6) and atomic structure of SRII (7-9) are well characterized. SRII bound to an N-terminal fragment of HtrII have provided atomic details of the two proteins' interaction surface in the periplasm and within the membrane (10), and interaction of the HtrII membrane-proximal domain with the cytoplasmic domain of the receptor has been demonstrated by fluorescent probe accessibility and Förster resonance energy transfer measurements (11), EPR of spin-labels (12), and in vitro binding of HtrII peptides to SRII (13). The signal relay mechanism from SRII to HtrII in the complex has become a focus of interest in part because of its importance to the general understanding of interaction between integral membrane proteins.The results from several different methods show that lightinduced structural changes occur all along the SRII-HtrII interface, which includes the region on the periplasmic side of the membrane, the membrane-embedded domain, and the cytoplasm...

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“…The FTIR measurements at 77 K revealed that only the C 14 -D stretching vibration at 2244 cm −1 is significantly enhanced upon formation of the K state. We interpreted that the steric constraint occurs at the C 14 D group in SRII K , where rotation of the C 13 =C 14 bond probably leads to the movement of the C 14 D group (9). It is noted that SRII K exhibits various HOOP vibrations, suggesting that the chromophore is widely distorted along the polyene chain (10).…”

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confidence: 91%

“…It is noted that SRII K exhibits various HOOP vibrations, suggesting that the chromophore is widely distorted along the polyene chain (10). In contrast to the HOOP bands, the C-D stretching vibration was specific for the C 14 group of SRII K (9). This fact implies that the C-D stretch provides structural information about the direct contact of the C 14 deuterium (hydrogen) with surroundings.…”

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confidence: 99%

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Steric Constraint in the Primary Photoproduct of Sensory Rhodopsin II Is a Prerequisite for Light-Signal Transfer to HtrII

et al. 2008

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Sensory rhodopsin II (SRII, also called pharaonis phoborhodopsin, ppR) is responsible for negative phototaxis in Natronomonas pharaonis. Photoisomerization of the retinal chromophore from all-trans to 13-cis initiates conformational changes in the protein, leading to activation of the cognate transducer protein (HtrII). We previously observed enhancement of the C 14 -D stretching vibration of the retinal chromophore at 2244 cm −1 upon formation of the K state and interpreted that a steric constraint occurs at the C 14 D group in SRII K . Here, we identify the counterpart of the C 14 D group as Thr204, because the C 14 -D stretching signal disappeared in T204A, T204S, and T204C mutants as well as a C 14 -HOOP (hydrogen out-of-plane) vibration at 864 cm −1 . Although the K state of the wild-type bacteriorhodopsin (BR), a light-driven proton pump, possesses neither 2244 nor 864 cm −1 bands, both signals appeared for the K state of a triple mutant of BR that functions as a light sensor (P200T/V210Y/A215T). We found a positive correlation between these vibrational amplitudes of the C 14 atom at 77 K and the physiological phototaxis response. These observations strongly suggest that the steric constraint between the C 14 group of retinal and Thr204 of the protein is a prerequisite for light-signal transduction by SRII.Microbial rhodopsins convert light into chemiosmotic energy or cellular signals (1, 2). The primary reaction is all-trans to 13-cis photoisomerization of the retinal chromophore, and light energy is stored through altered chromophore-protein interaction (2, 3). Such energy is subsequently consumed by changing the protein structures, and ion pumping or transducer activation is achieved in light-energy or signal conversions, respectively. It is well-known that retinal isomerization in the protein is a selective and efficient reaction along the

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Steric Constraint in the Primary Photoproduct of an Archaeal Rhodopsin from Regiospecific Perturbation of C−D Stretching Vibration of the Retinyl Chromophore

Cited by 41 publications

References 42 publications

Three strategically placed hydrogen-bonding residues convert a proton pump into a sensory receptor

Three strategically placed hydrogen-bonding residues convert a proton pump into a sensory receptor

Functional Importance of the Interhelical Hydrogen Bond between Thr204 and Tyr174 of Sensory Rhodopsin II and Its Alteration during the Signaling Process

Steric Constraint in the Primary Photoproduct of Sensory Rhodopsin II Is a Prerequisite for Light-Signal Transfer to HtrII

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