Hydrogen Bonds of Protein‐Bound Water Molecules in Rhodopsins

Kandori, Hideki

doi:10.1002/9780470669143.ch18

Cited by 7 publications

(8 citation statements)

References 64 publications

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“…These results indicate that the protonated Schiff base forms a strong hydrogen bond with a water molecule, which is connected to Asp75 with a weak hydrogen bond. This result with ASR supports the working hypothesis by our group about the strong correlation between the proton pump activity and the existence of strongly hydrogen bonded water molecules in microbial rhodopsins (Furutani et al, 2005b;Shibata et al, 2005Shibata et al, , 2007Kandori, 2006Kandori, , 2010.…”

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confidence: 92%

An inward proton transport using anabaena sensory rhodopsin

et al. 2011

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ATP is synthesized by an enzyme that utilizes proton motive force and thus nature creates various proton pumps. The best understood proton pump is bacteriorhodopsin (BR), an outward-directed light-driven proton pump in Halobacterium salinarum. Many archaeal and eubacterial rhodopsins are now known to show similar proton transport activity. Proton pumps must have a specific mechanism to exclude transport in the reverse direction to maintain a proton gradient, and in the case of BR, a highly hydrophobic cytoplasmic domain may constitute such machinery. Although an inward proton pump has neither been created naturally nor artificially, we recently reported that an inward-directed proton transport can be engineered from a bacterial rhodopsin by a single amino acid replacement Anabaena sensory rhodopsin (ASR) is a photochromic sensor in freshwater cyanobacteria, possessing little proton transport activity. When we replace Asp217 at the cytoplasmic domain (distance ∼ 15 Å from the retinal chromophore) to Glu, ASR is converted into an inward proton transport, driven by absorption of a single photon. FTIR spectra clearly show an increased proton affinity for Glu217, which presumably controls the unusual directionality opposite to normal proton pumps.

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confidence: 92%

An inward proton transport using anabaena sensory rhodopsin

et al. 2011

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“…Such water-containing hydrogen-bonding network must play important functional role. In fact, we found strong correlation between the hydrogen-bonding strength of such water molecules and proton-pumping activity of rhodopsins 6 , 26 , 27 .…”

Section: Resultsmentioning

confidence: 78%

“…One exception is seen for photoreceptive proteins, whose transient intermediates can be trapped at low temperatures or kinetically resolved in a time-dependent manner. In fact, we have shown that light-induced difference Fourier-transform infrared (FTIR) spectroscopy is a powerful tool to monitor functional water molecules in photoreceptive proteins such as rhodopsins 2 , 5 , 6 . In the measurements, we prepare hydrated films of proteins, by which water content in the sample can be significantly reduced 7 , 8 .…”

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confidence: 99%

Detection of a protein-bound water vibration of halorhodopsin in aqueous solution

2013

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Protein-bound water molecules play crucial roles in their structure and function, but their detection is an experimental challenge, particularly in aqueous solution at room temperature. By applying attenuated total reflection (ATR) Fourier-transform infrared (FTIR) spectroscopy to a light-driven Cl− pump pharaonis halorhodopsin (pHR), here we detected an O-H stretching vibration of protein-bound water molecules in the active center. The pHR(Cl−) minus pHR(Br−) ATR-FTIR spectra show random fluctuation at 3600–3000 cm−1, frequency window of water vibration, which can be interpreted in terms of dynamical fluctuation of aqueous water at room temperature. On the other hand, we observed a reproducible spectral feature at 3617 (+)/3630 (−) cm−1 in the pHR(Cl−) minus pHR(Br−) spectrum, which is absent in the pHR(Cl−) minus pHR(Cl−) and in the pHR(Br−) minus pHR(Br−) spectra. The water O-H stretching vibrations of pHR(Cl−) and pHR(Br−) at 3617 and 3630 cm−1, respectively, are confirmed by light-induced difference FTIR spectra in isotope water (H218O) at 77 K. The observed water molecule presumably binds to the active center of pHR, and alter its hydrogen bond during the Cl− pumping photocycle.

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“…The significant difference in the lowest O-D stretching frequency implies that the H-bond properties of W402 are significantly different in BR and ASR. It has been established by FTIR that the lowest O-D stretching frequency of water can be found at less than 2400 cm Ϫ1 in a number of proton-pumping rhodopsins (12). The same tendency also holds true for BR and ASR.…”

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confidence: 74%

Factors That Differentiate the H-bond Strengths of Water Near the Schiff Bases in Bacteriorhodopsin and Anabaena Sensory Rhodopsin

Saito

Kandori

Ishikita

2012

Journal of Biological Chemistry

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Background: Bacteriorhodopsin (BR) functions as a proton pump, whereas Anabaena sensory rhodopsin (ASR) functions as a photosensor. Results: pK a of the conserved Asp residues near the Schiff base significantly differ between BR and ASR. Conclusion:The O-D stretching frequencies for D 2 O are correlated with pK a (Asp). Significance: The presence of a strongly H-bonded water results from the proton-pumping activity in BR.

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Hydrogen Bonds of Protein‐Bound Water Molecules in Rhodopsins

Cited by 7 publications

References 64 publications

An inward proton transport using anabaena sensory rhodopsin

An inward proton transport using anabaena sensory rhodopsin

Detection of a protein-bound water vibration of halorhodopsin in aqueous solution

Factors That Differentiate the H-bond Strengths of Water Near the Schiff Bases in Bacteriorhodopsin and Anabaena Sensory Rhodopsin

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