Sensory rhodopsin I photocycle intermediate SRI<sub>380</sub> contains 13‐<i>cis</i> retinal bound via an unprotonated Schiff base

Haupts, Ulrich; Eisfeld, W.; Stockburger, Manfred; Oesterhelt, Dieter

doi:10.1016/0014-5793(94)01226-1

Cited by 22 publications

(35 citation statements)

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“…However, the dark state isomer configuration of the retinylidene chromophore in the wild-type SRI-HtrI complex is all trans, with no detectable 13-cis isomer present (46). Like the all trans isomeric forms of BR and ASR (47), upon formation of M, SRI undergoes all trans to 13-cis photoisomerization in both free and complex form (48). FTIR spectroscopy does not show significant differences between the wild-type complex and inverted SRI-HtrIE56Q mutant complex in reconstituted liposomes (O.A.S., J.S., B.J.P., J.L.S., and Hideki Kandori, unpublished data).…”

Section: Discussionmentioning

confidence: 99%

A Schiff base connectivity switch in sensory rhodopsin signaling

Sineshchekov

Sasaki

Phillips

et al. 2008

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

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Section: Discussionmentioning

confidence: 99%

A Schiff base connectivity switch in sensory rhodopsin signaling

Sineshchekov

Sasaki

Phillips

et al. 2008

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

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“…Formation of S 373 is accompanied by release of the proton from the Schiff base nitrogen in the attachment site of the retinal within the photoactive site of SRI (Haupts et al ., 1994). A proton returns to the Schiff base nitrogen in the second half of the photocycle during the thermal S 373 to SR 587 conversion.…”

Section: Htri Blocks a Cytoplasmic Half‐channel In Srimentioning

confidence: 99%

Variations on a molecular switch: transport and sensory signalling by archaeal rhodopsins

Spudich¹

1998

Molecular Microbiology

134

111

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SummaryThe archaeal rhodopsins are a family of seven-transmembrane-helix, visual pigment-like proteins found in Halobacterium salinarum and related halophilic Archaea. Two, bacteriorhodopsin (BR) and halorhodopsin (HR), are transport rhodopsins that carry out light-driven electrogenic translocation of protons and chloride, respectively, across the cell membrane. The other two, sensory rhodopsins I and II (SRI and SRII), are phototaxis receptors that send signals to tightly bound transducer proteins that in turn control a phosphorylation cascade modulating the cell's flagellar motors. Recent progress has cast light on how nature has modified the common design of these proteins to carry out their distinctly different functions: electrogenic ion transport and non-electrogenic signal transduction. A key shared mechanism between BR and SRII appears to be an interhelical salt bridge locked conformational switch that is released by photoisomerization of retinal. In BR disruption of the lock opens a cytoplasmic half-channel that ensures uptake of the transported proton from the cytoplasmic side of the membrane at a critical time in the pumping cycle. Transducer-free SRI uses the same mechanism to carry out light-driven proton transport, but interaction with its transducer blocks the cytoplasmic half-channel thereby interrupting the transport cycle. In SRI, transducer interaction also disrupts the salt bridge in the dark, poising the receptor in an intermediate conformation able to produce opposite signals depending on the colour of the stimulus light. A model for signalling is proposed in which the salt bridge-controlled half-channel is used to modulate interaction with the Htr proteins when the receptor signalling states are formed.

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“…The SRI amino acid sequence (9) reveals a striking degree of sequence homology to BR (10) and HR (11), suggesting seven transmembrane helices (A-G) as found for BR (12) and HR (13). Retinal is bound as a protonated Schiff base (14,15) to Lys-206 in helix G of SRI. In BR Asp-85 and Asp-96 function as proton acceptor and donor, respectively (16-18).…”

Section: Introductionmentioning

confidence: 99%

“…Retinal is bound as a protonated Schiff base (14,15) to in helix G of SRI. In BR Asp-85 and Asp-96 function as proton acceptor and donor, respectively (16)(17)(18).…”

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The photoreceptor sensory rhodopsin I as a two-photon-driven proton pump.

Haupts

Oesterhelt

1995

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

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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 SRI amino acid sequence (9) reveals a striking degree of sequence homology to BR (10) and HR (11), suggesting seven transmembrane helices (A-G) as found for BR (12) and HR (13). Retinal is bound as a protonated Schiff base (14,15) to Lys-206 in helix G of SRI. In BR Asp-85 and Asp-96 function as proton acceptor and donor, respectively (16-18).The absence of one or both of these residues renders the proton pump inefficient for phototrophic growth, because turnover rates drop from about 100 s-1 to 1 s-1 in the case of the Asp-96 -> Asn mutation, whereas in Asp-85 -* Xaa mutants, M formation (deprotonation of the Schiff base) is prevented. In SRI the corresponding positions are occupied byThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.Asp-76 and Tyr-87; i.e., the amino acid functioning as acceptor in BR is retained while the donor site is replaced by tyrosine, thus explaining the low turnover rate of the SRI photocycle. In addition, Fourier transform IR spectroscopy studies (19,20) have shown that Asp-76 is protonated in the initial state as well as in SRI380, undergoing only a change in environment during the transition. A possible ion translocation activity of SRI could not be excluded on this basis, because BR mutants lacking both donor and acceptor side chain are still active at a low level of transport rates in a two-photon process (21). However, a previous study of SRI photocycling (22) did not detect any electrogenic activity of SRI.Until recently, experiments on SRI were carried out with wild-type cells and derived membrane fractions where SRI occurs as a stoichiometric complex with its transducer protein . The thermal decay of SRI380 is independent of bulk pH in the case of the HtrI-SRI complex, while an exponential increase in the decay time of SRI380 with increasing pH is observed for SRI alone. In the case of Htr-deficient SRI, the formation of SRI380 can be correlated with the appearance of one proton in the bulk medium per SRI380 formed (26), but at the same time the recovery of the initial state is slowed to about 30 s at pH 7 (27). Thus, a one-photon process could only drive proton translocation at very slow speed but a two-photon process might be efficient enough to be detected in intact cells by standard techniques.Here we report the results of experiments with cells overproducing HtrI-free SRI by a factor of 50 (28). SRI is indeed shown to be active in proton translocation in a two-photondriven process involving the two photocycle intermediates SRI380 and SRI520.MATERIALS AND METHODS Bacterial Strains. H. salinarium strain Q6, used for transport experiments and cell membrane preparations, is a SRIoverproducing strain which has been constructed by tra...

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Sensory rhodopsin I photocycle intermediate SRI₃₈₀ contains 13‐cis retinal bound via an unprotonated Schiff base

Cited by 22 publications

References 29 publications

A Schiff base connectivity switch in sensory rhodopsin signaling

A Schiff base connectivity switch in sensory rhodopsin signaling

Variations on a molecular switch: transport and sensory signalling by archaeal rhodopsins

The photoreceptor sensory rhodopsin I as a two-photon-driven proton pump.

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Sensory rhodopsin I photocycle intermediate SRI380 contains 13‐cis retinal bound via an unprotonated Schiff base

Cited by 22 publications

References 29 publications

A Schiff base connectivity switch in sensory rhodopsin signaling

A Schiff base connectivity switch in sensory rhodopsin signaling

Variations on a molecular switch: transport and sensory signalling by archaeal rhodopsins

The photoreceptor sensory rhodopsin I as a two-photon-driven proton pump.

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Sensory rhodopsin I photocycle intermediate SRI₃₈₀ contains 13‐cis retinal bound via an unprotonated Schiff base