Structural insights into the early steps of receptor-transducer signal transfer in archaeal phototaxis

Wegener, Ansgar-A.; Klare, Johann P.; Engelhard, Martin; Steinhoff, Heinz‐Jürgen

doi:10.1093/emboj/20.19.5312

Cited by 173 publications

(260 citation statements)

References 32 publications

(56 reference statements)

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“…Site-directed spin labeling measurements revealed a lightinduced transient decrease of nitroxide mobility in SRII S158C-R1 which faces HtrII TM2 (where R1 indicates the spin label attached to the Cys residue) and an increase in mobility of the probe attached at L159C, which faces away from TM2 on helix F. These results were interpreted as a movement of the helix toward TM2 of HtrII during activation (15,16). This movement fits well with the model suggested here.…”

Section: Discussionsupporting

confidence: 84%

“…Light-induced tilting of helix F (and to a lesser extent helix G) opens a cytoplasmic channel in BR (14) and this tilting has been shown to occur in SRII both when free and bound to HtrII (15,16), with HtrII inhibiting the proton uptake through the channel as in the SRI-HtrI complex. This conformational change, which involves structural alterations mainly in the cytoplasmic end of helix F and in the E-F loop (14), has been proposed based on several lines of evidence to be responsible for activating the Htr transducers (17).…”

mentioning

confidence: 99%

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The Cytoplasmic Membrane-proximal Domain of the HtrII Transducer Interacts with the E-F Loop of Photoactivated Natronomonas pharaonis Sensory Rhodopsin II

Yang

Sineshchekov²,

Spudich

et al. 2004

Journal of Biological Chemistry

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The structures of the cytoplasmic loops of the phototaxis receptor sensory rhodopsin II (SRII) and the membrane-proximal cytoplasmic domain of its bound transducer HtrII were examined in the dark and in the lightactivated state by fluorescent probes and cysteine crosslinking. Light decreased the accessibility of E-F loop position 154 in the SRII-HtrII complex, but not in free SRII, consistent with HtrII proximity, which was confirmed by tryptophans placed within a 5-residue region identified in the HtrII membrane-proximal domain that exhibited Fö rster resonance energy transfer to a fluorescent probe at position 154 in SRII. The Fö rster resonance energy transfer was eliminated in the signaling deficient HtrII mutant G83F without loss of affinity for SRII. Finally, the presence of SRII and HtrII reciprocally inhibit homodimer disulfide cross-linking reactions in their membrane-proximal domains, showing that each interferes with the others self-interaction in this region. The results demonstrate close proximity between SRII-HtrII in the membrane-proximal domain, and in addition, light stimulation of the SRII inhibition of HtrII cross-linking was observed, indicating that the contact is enhanced in the photoactivated complex. A mechanism is proposed in which photoactivation alters the SRII-HtrII interaction in the membrane-proximal region during the signal relay process.Archaeal sensory rhodopsins I and II (SRI and SRII) 1 are membrane-embedded phototaxis receptors that modulate the motility apparatus of Halobacterium salinarum and related haloarchaeal species (1-3). The SRI and SRII proteins transmit signals to their cognate transducer proteins, HtrI and HtrII, respectively, and like their eubacterial counterparts in chemotaxis, the Htr transducers control a histidine kinase and phosphoregulator protein that modulates motor function.Biochemical and spectroscopic studies have shown that there is close interaction between the SR and Htr components of the signaling complex both in the light and in the dark (1); i.e. they are subunits of a molecular complex. Furthermore, chimera experiments demonstrated that the interaction specificities of SRI with HtrI and SRII with HtrII are determined by the transmembrane helices of the Htr subunits (4). Cubic lipid phase crystal x-ray structures of SRII have defined the membrane-embedded and membrane-external portions of the transmembrane helices and periplasmic and cytoplasmic loops of the protein (5, 6). Moreover, co-crystallization of SRII with an N-terminal fragment of HtrII containing its two transmembrane segments (TM1 and TM2) and a cytoplasmic extension of TM2 provided an atomic resolution structure by x-ray diffraction (7). The structure resolved extensive van der Waals and hydrogen-bonding contacts between HtrII TM2 (and to a lesser extent TM1) and SRII helices F and G within the membrane domain. The presence of the cytoplasmic membrane-proximal domain, comprised of 32 residues beyond Leu-82 at the membrane-cytoplasm interface, was necessary for high affinity binding o...

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Section: Discussionsupporting

confidence: 84%

mentioning

confidence: 99%

The Cytoplasmic Membrane-proximal Domain of the HtrII Transducer Interacts with the E-F Loop of Photoactivated Natronomonas pharaonis Sensory Rhodopsin II

Yang

Sineshchekov²,

Spudich

et al. 2004

Journal of Biological Chemistry

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“…RMSD of coordinates are 0.53 Å for 1H2S 5 28,29 . EPR experiments also show that reordering of helix F and TM2 occurs, believed to represent the signal, occurs concomitantly with O-decay 6 . FTIR studies [30][31][32] indicate, that the more active state is present in the crystal, the larger are the diffraction resolution losses.…”

Section: Structure Of the Ground Statementioning

confidence: 88%

“…In the cellular membrane NpSRII is bound to its cognate transducer NpHtrII in a 2:2 complex 5,6 to form the signaling module.…”

Section: Introductionmentioning

confidence: 99%

“…The functionally important conformational step occurs during the M1→M2 transition which leads to the signaling state 7,8 . During this transition the signal is transferred through the interface comprising helices F and G to NpHtrII, which results in a rotary motion of transmembrane helix TM2 6,9 . This activation occurs at the level of the membrane.…”

Section: Introductionmentioning

confidence: 99%

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Active State of Sensory Rhodopsin II: Structural Determinants for Signal Transfer and Proton Pumping

Gushchin

Reshetnyak

Borshchevskiy

et al. 2011

Journal of Molecular Biology

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The molecular mechanism of transmembrane signal transduction is still a pertinent question in cellular biology. Generally, a receptor can transfer an external signal via its cytoplasmic surface as found for GPCRs like rhodopsin or via the membrane domain like it is utilized by sensory rhodopsin II (SRII) in complex with its transducer HtrII. In the absence of HtrII SRII functions as a proton pump. Here, we report on the crystal structure of the active state of SRII from Natronomonas pharaonis (NpSRII). The problem of a dramatic loss of the diffraction quality upon loading of the active state was overcome by growing better crystals and reducing the occupancy of the state. The determined conformational changes at the region comprising helices F and G are similar to those observed for the NpSRII-transducer complex but they are much more pronounced. Meaning of these differences for proton pumping ability and understanding of the signal transduction by NpSRII is discussed.

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Key determinants for signaling in the sensory rhodopsin II/transducer complex are different between Halobacterium salinarum and Natronomonas pharaonis

Matsunami‐Nakamura,

Tamogami,

Takeguchi

et al. 2023

FEBS Letters

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The cell membrane of Halobacterium salinarum contains a retinal‐binding photoreceptor, sensory rhodopsin II (HsSRII), coupled with its cognate transducer (HsHtrII), allowing repellent phototaxis behavior for shorter wavelength light. Previous studies on SRII from Natronomonas pharaonis (NpSRII) pointed out the importance of the hydrogen bonding interaction between Thr204NpSRII and Tyr174NpSRII in signal transfer from SRII to HtrII. Here, we investigated the effect on phototactic function by replacing residues in HsSRII corresponding to Thr204NpSRII and Tyr174NpSRII. Whereas replacement of either residue altered the photocycle kinetics, introduction of any mutations at Ser201HsSRII and Tyr171HsSRII did not eliminate negative phototaxis function. These observations imply the possibility of the presence of an unidentified molecular mechanism for photophobic signal transduction differing from NpSRII–NpHtrII.

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Structural insights into the early steps of receptor-transducer signal transfer in archaeal phototaxis

Cited by 173 publications

References 32 publications

The Cytoplasmic Membrane-proximal Domain of the HtrII Transducer Interacts with the E-F Loop of Photoactivated Natronomonas pharaonis Sensory Rhodopsin II

The Cytoplasmic Membrane-proximal Domain of the HtrII Transducer Interacts with the E-F Loop of Photoactivated Natronomonas pharaonis Sensory Rhodopsin II

Active State of Sensory Rhodopsin II: Structural Determinants for Signal Transfer and Proton Pumping

Key determinants for signaling in the sensory rhodopsin II/transducer complex are different between Halobacterium salinarum and Natronomonas pharaonis

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