Changes in the hydrogen-bonding strength of internal water molecules and cysteine residues in the conductive state of channelrhodopsin-1

Lórenz-Fonfrı́a, Vı́ctor A.; Muders, Vera; Schlesinger, Ramona; Heberle, Joachim

doi:10.1063/1.4895796

Cited by 42 publications

(72 citation statements)

References 107 publications

(133 reference statements)

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“…3). Although not identical, these spectra are also similar to recently reported FTIR difference spectra recorded at room temperature of CaChR1 in detergent micelles (25,26).…”

Section: Ftir Difference Spectroscopy Of the Cachr1 3 P 2 380 Transitionsupporting

confidence: 72%

Proton Transfers in a Channelrhodopsin-1 Studied by Fourier Transform Infrared (FTIR) Difference Spectroscopy and Site-directed Mutagenesis

Ogren

Mamaev

et al. 2015

Journal of Biological Chemistry

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Background: Channelrhodopsin-1 is a red-shifted light-gated cation channel. Results: Proton transfers and H-bonding changes involving the Schiff base counterion residues Asp-169 and Glu-299 were detected. Conclusion: A two-step proton transfer relay mechanism consistent with our results and earlier photoinduced channel current and pH titration measurements is proposed. Significance: Understanding the mechanism of channelrhodopsin can lead to improved optogenetic control of neurons.

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“…3). Although not identical, these spectra are also similar to recently reported FTIR difference spectra recorded at room temperature of CaChR1 in detergent micelles (25,26).…”

Section: Ftir Difference Spectroscopy Of the Cachr1 3 P 2 380 Transitionsupporting

confidence: 72%

Proton Transfers in a Channelrhodopsin-1 Studied by Fourier Transform Infrared (FTIR) Difference Spectroscopy and Site-directed Mutagenesis

Ogren

Mamaev

et al. 2015

Journal of Biological Chemistry

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“…This view is common for Cr CCR2 [23,24,29], the most studied ChR. In contrast, a smaller change of amide-I was reported for Ca CCR1 at 80 K [33], and a time-resolved FTIR study of Ca CCR1 reported large changes of amide-I occurring in later intermediates [32]. Thus, limited protein structural changes to Gt CCR4 upon retinal photoisomerization are similar to Ca CCR1, but not to Cr CCR2.…”

Section: Resultsmentioning

confidence: 96%

Molecular properties of a DTD channelrhodopsin from <i>Guillardia theta</i>

et al. 2017

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Microbial rhodopsins are membrane proteins found widely in archaea, eubacteria and eukaryotes (fungal and algal species). They have various functions, such as light-driven ion pumps, light-gated ion channels, light sensors and light-activated enzymes. A light-driven proton pump bacteriorhodopsin (BR) contains a DTD motif at positions 85, 89, and 96, which is unique to archaeal proton pumps. Recently, channelrhodopsins (ChRs) containing the DTD motif, whose sequential identity is ~20% similar to BR and to cation ChRs in Chlamydomonas reinhardtii (CrCCRs), were found. While extensive studies on ChRs have been performed with CrCCR2, the molecular properties of DTD ChRs remain an intrigue. In this paper, we studied a DTD rhodopsin from G. theta (GtCCR4) using electrophysiological measurements, flash photolysis, and low-temperature difference FTIR spectroscopy. Electrophysiological measurements clearly showed that GtCCR4 functions as a light-gated cation channel, similar to other G. theta DTD ChRs (GtCCR1-3). Light-driven proton pump activity was also suggested for GtCCR4. Both electrophysiological and flash photolysis experiments showed that channel closing occurs upon reprotonation of the Schiff base, suggesting that the dynamics of retinal and channels are tightly coupled in GtCCR4. From Fourier transform infrared (FTIR) spectroscopy at 77 K, we found that the primary reaction is an all-trans to a 13-cis photoisomerization, like other microbial rhodopsins, although perturbations in the secondary structure were much smaller in GtCCR4 than in CrCCR2.

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“…For example, extensive time-resolved visible and FTIR difference studies have been performed on BR 42 and more recently Cr ChR2. 8,33,43–49 In one study, time-resolved FTIR and UV–vis difference spectroscopy combined with MSD calculation led to the proposal that a downward movement of Glu90 (homologue of Glu68 in Gt ACR1) causes helix 2 to tilt downward, thereby resulting in channel opening. 44 …”

Section: Discussionmentioning

confidence: 99%

Structural Changes in an Anion Channelrhodopsin: Formation of the K and L Intermediates at 80 K

Hai

Mamaeva

et al. 2017

Biochemistry

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A recently discovered natural family of light-gated anion channelrhodopsins (ACRs) from cryptophyte algae provides an effective means of optogenetically silencing neurons. The most extensively studied ACR is from Guillardia theta (GtACR1). Earlier studies of GtACR1 have established a correlation between formation of a blue-shifted L-like intermediate and the anion channel “open” state. To study structural changes of GtACR1 in the K and L intermediates of the photocycle, a combination of low-temperature Fourier transform infrared (FTIR) and ultraviolet–visible absorption difference spectroscopy was used along with stable-isotope retinal labeling and site-directed mutagenesis. In contrast to bacteriorhodopsin (BR) and other microbial rhodopsins, which form only a stable red-shifted K intermediate at 80 K, GtACR1 forms both stable K and L-like intermediates. Evidence includes the appearance of positive ethylenic and fingerprint vibrational bands characteristic of the L intermediate as well as a positive visible absorption band near 485 nm. FTIR difference bands in the carboxylic acid C=O stretching region indicate that several Asp/Glu residues undergo hydrogen bonding changes at 80 K. The Glu68 → Gln and Ser97 → Glu substitutions, residues located close to the retinylidene Schiff base, altered the K:L ratio and several of the FTIR bands in the carboxylic acid region. In the case of the Ser97 → Glu substitution, a significant red-shift of the absorption wavelength of the K and L intermediates occurs. Sequence comparisons suggest that L formation in GtACR1 at 80 K is due in part to the substitution of the highly conserved Leu or Ile at position 93 in helix 3 (BR sequence) with the homologous Met105 in GtACR1.

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Changes in the hydrogen-bonding strength of internal water molecules and cysteine residues in the conductive state of channelrhodopsin-1

Cited by 42 publications

References 107 publications

Proton Transfers in a Channelrhodopsin-1 Studied by Fourier Transform Infrared (FTIR) Difference Spectroscopy and Site-directed Mutagenesis

Proton Transfers in a Channelrhodopsin-1 Studied by Fourier Transform Infrared (FTIR) Difference Spectroscopy and Site-directed Mutagenesis

Molecular properties of a DTD channelrhodopsin from <i>Guillardia theta</i>

Structural Changes in an Anion Channelrhodopsin: Formation of the K and L Intermediates at 80 K

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