FTIR Analysis of the SII540Intermediate of Sensory Rhodopsin II:  Asp73 Is the Schiff Base Proton Acceptor†

Biochemistry ◽  
2000 ◽  
Vol 39 (11) ◽  
pp. 2823-2830 ◽  
Author(s):  
Vladislav Bergo ◽  
Elena N. Spudich ◽  
Kenneth L. Scott ◽  
John L. Spudich ◽  
Kenneth J. Rothschild
Keyword(s):  
Schiff Base ◽  
Proton Acceptor ◽  
Ftir Analysis ◽  
Sensory Rhodopsin

scholarly journals His166 Is the Schiff Base Proton Acceptor in Attractant Phototaxis Receptor Sensory Rhodopsin I

Biochemistry ◽  
2014 ◽  
Vol 53 (37) ◽  
pp. 5923-5929 ◽  
Author(s):  
Jun Sasaki ◽  
Hazuki Takahashi ◽  
Yuji Furutani ◽  
Oleg A. Sineshchekov ◽  
John L. Spudich ◽  
...  
Keyword(s):  
Schiff Base ◽  
Proton Acceptor ◽  
Sensory Rhodopsin ◽  
Sensory Rhodopsin I

Asp76 Is the Schiff Base Counterion and Proton Acceptor in the Proton-Translocating Form of Sensory Rhodopsin I†

Biochemistry ◽  
1996 ◽  
Vol 35 (21) ◽  
pp. 6690-6696 ◽  
Author(s):  
Parshuram Rath ◽  
Elena Spudich ◽  
Dearl D. Neal ◽  
John L. Spudich ◽  
Kenneth J. Rothschild
Keyword(s):  
Schiff Base ◽  
Proton Acceptor ◽  
Sensory Rhodopsin ◽  
Sensory Rhodopsin I

Probing Ultrafast Photochemistry of Retinal Proteins in the Near-IR: Bacteriorhodopsin and Anabaena Sensory Rhodopsin vs Retinal Protonated Schiff Base in Solution

2012 ◽  
Vol 117 (16) ◽  
pp. 4670-4679 ◽  
Author(s):  
Amir Wand ◽  
Boris Loevsky ◽  
Noga Friedman ◽  
Mordechai Sheves ◽  
Sanford Ruhman
Keyword(s):  
Schiff Base ◽  
Sensory Rhodopsin ◽  
Near Ir ◽  
Retinal Proteins

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

FEBS Letters ◽  
1994 ◽  
Vol 356 (1) ◽  
pp. 25-29 ◽  
Author(s):  
Ulrich Haupts ◽  
Wolf Eisfeld ◽  
Manfred Stockburger ◽  
Dieter Oesterhelt
Keyword(s):  
Schiff Base ◽  
Sensory Rhodopsin ◽  
Sensory Rhodopsin I

scholarly journals Photochemical reaction cycle transitions during anion channelrhodopsin gating

2016 ◽  
Vol 113 (14) ◽  
pp. E1993-E2000 ◽  
Author(s):  
Oleg A. Sineshchekov ◽  
Hai Li ◽  
Elena G. Govorunova ◽  
John L. Spudich
Keyword(s):  
Schiff Base ◽  
Hek293 Cells ◽  
Proton Acceptor ◽  
Channel Activity ◽  
Wild Type ◽  
Anion Selectivity ◽  
Slow Channel ◽  
Guillardia Theta ◽  
Report Analysis ◽  
Ion Conducting

A recently discovered family of natural anion channelrhodopsins (ACRs) have the highest conductance among channelrhodopsins and exhibit exclusive anion selectivity, which make them efficient inhibitory tools for optogenetics. We report analysis of flash-induced absorption changes in purified wild-type and mutant ACRs, and of photocurrents they generate in HEK293 cells. Contrary to cation channelrhodopsins (CCRs), the ion conducting state of ACRs develops in an L-like intermediate that precedes the deprotonation of the retinylidene Schiff base (i.e., formation of an M intermediate). Channel closing involves two mechanisms leading to depletion of the conducting L-like state: (i) Fast closing is caused by a reversible L⇔M conversion. Glu-68 in Guillardia theta ACR1 plays an important role in this transition, likely serving as a counterion and proton acceptor at least at high and neutral pH. Incomplete suppression of M formation in the GtACR1_E68Q mutant indicates the existence of an alternative proton acceptor. (ii) Slow closing of the channel parallels irreversible depletion of the M-like and, hence, L-like state. Mutation of Cys-102 that strongly affected slow channel closing slowed the photocycle to the same extent. The L and M intermediates were in equilibrium in C102A as in the WT. In the position of Glu-123 in channelrhodopsin-2, ACRs contain a noncarboxylate residue, the mutation of which to Glu produced early Schiff base proton transfer and strongly inhibited channel activity. The data reveal fundamental differences between natural ACR and CCR conductance mechanisms and their underlying photochemistry, further confirming that these proteins form distinct families of rhodopsin channels.

scholarly journals Retinal isomerization and water-pore formation in channelrhodopsin-2

2018 ◽  
Vol 115 (14) ◽  
pp. 3557-3562 ◽  
Author(s):  
Albert Ardevol ◽  
Gerhard Hummer
Keyword(s):  
Schiff Base ◽  
Conformational Changes ◽  
Pore Formation ◽  
Proton Acceptor ◽  
Time Resolved ◽  
Channel Opening ◽  
Selective Channel ◽  
Extracellular Side ◽  
Membrane Spanning ◽  
Time Resolved Infrared Spectroscopy

Channelrhodopsin-2 (ChR2) is a light-sensitive ion channel widely used in optogenetics. Photoactivation triggers a trans-to-cis isomerization of a covalently bound retinal. Ensuing conformational changes open a cation-selective channel. We explore the structural dynamics in the early photocycle leading to channel opening by classical (MM) and quantum mechanical (QM) molecular simulations. With QM/MM simulations, we generated a protein-adapted force field for the retinal chromophore, which we validated against absorption spectra. In a 4-µs MM simulation of a dark-adapted ChR2 dimer, water entered the vestibules of the closed channel. Retinal all-trans to 13-cis isomerization, simulated with metadynamics, triggered a major restructuring of the charge cluster forming the channel gate. On a microsecond time scale, water penetrated the gate to form a membrane-spanning preopen pore between helices H1, H2, H3, and H7. This influx of water into an ion-impermeable preopen pore is consistent with time-resolved infrared spectroscopy and electrophysiology experiments. In the retinal 13-cis state, D253 emerged as the proton acceptor of the Schiff base. Upon proton transfer from the Schiff base to D253, modeled by QM/MM simulations, we obtained an early-M/P2390–like intermediate. Rapid rotation of the unprotonated Schiff base toward the cytosolic side effectively prevents its reprotonation from the extracellular side. From MM and QM simulations, we gained detailed insight into the mechanism of ChR2 photoactivation and early events in pore formation. By rearranging the network of charges and hydrogen bonds forming the gate, water emerges as a key player in light-driven ChR2 channel opening.

scholarly journals Correlation of the O-Intermediate Rate with the pKa of Asp-75 in the Dark, the Counterion of the Schiff Base of Pharaonis Phoborhodopsin (Sensory Rhodopsin II)

2005 ◽  
Vol 88 (2) ◽  
pp. 1215-1223 ◽  
Author(s):  
Masayuki Iwamoto ◽  
Yuki Sudo ◽  
Kazumi Shimono ◽  
Tsunehisa Araiso ◽  
Naoki Kamo
Keyword(s):  
Schiff Base ◽  
Sensory Rhodopsin ◽  
Intermediate Rate
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