Kinetic isotope effects in the photochemical reaction cycle of ion transporting retinal proteins

Szakács, Juliánna; Lakatos, Melinda; Ganea, Constanţa; Váró, György

doi:10.1016/j.jphotobiol.2005.01.001

Cited by 7 publications

(10 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The time constants derived in this work are about a factor of 2 higher (Table 2) than the results obtained for PR in H 2 O buffer (17,18). This can be attributed to the kinetic isotope effect by H/D exchange and is in agreement with kinetic studies of the ion pumps BR, HR, and PR by Szakács et al (24). They found that transitions that do not require large H-bond rearrangements and/or proton motions show a moderate isotope effect of a factor of 1.5-2.…”

Section: à1 -1650 CM à1 (C¼n Stretching Region)supporting

confidence: 91%

“…As the IR measurements were carried out in D 2 O, also transient absorption experiments in the visible range were carried out, giving further information on the retinal dynamics under D 2 O conditions. This also allows a direct comparison of the experiments in the IR and in the vis spectral range, accounting for changes in the reaction rates by a factor of ;2 due to isotope effects as has been reported by Szakacs et al (24) MATERIALS AND METHODS…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Initial Reaction Dynamics of Proteorhodopsin Observed by Femtosecond Infrared and Visible Spectroscopy

Neumann

Verhoefen

Weber

et al. 2008

Biophysical Journal

View full text Add to dashboard Cite

We present a comparative study using femtosecond pump/probe spectroscopy in the visible and infrared of the early photodynamics of solubilized proteorhodopsin (green absorbing variant) in D(2)O with deprotonated (pD 9.2) and protonated (pD 6.4) primary proton acceptor Asp-97. The vis-pump/vis-probe experiments show a kinetic isotope effect that is more pronounced for alkaline conditions, thus decreasing the previously reported pH-dependence of the primary reaction of proteorhodopsin in H(2)O. This points to a pH dependent H-bonding network in the binding pocket of proteorhodopsin, that directly influences the primary photo-induced dynamics. The vis-pump/IR-probe experiments were carried out in two different spectral regions and allowed to monitor the retinal C=C (1500 cm(-1)-1580 cm(-1)) and C=N stretching vibration as well as the amide I mode of the protein (1590 cm(-1)-1680 cm(-1)). Like the FTIR spectra of the K intermediate (PR(K)-PR difference spectra) in this spectral range, the kinetic parameters and also the quantum efficiency of photo-intermediate formation are found to be virtually independent of the pD value.

show abstract

Section: à1 -1650 CM à1 (C¼n Stretching Region)supporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Initial Reaction Dynamics of Proteorhodopsin Observed by Femtosecond Infrared and Visible Spectroscopy

Neumann

Verhoefen

Weber

et al. 2008

Biophysical Journal

View full text Add to dashboard Cite

show abstract

“…Delayed decay of the M‐like intermediate at pH values above 9 has been observed by other groups for PR in lipid environment too, but the magnitude of the effect varies considerably . This may depend on sample composition or preparation.…”

Section: Discussionmentioning

confidence: 65%

Proteorhodopsin Photocycle Kinetics Between pH 5 and pH 9

Köhler

Weber

Glaubitz

et al. 2017

Photochem & Photobiology

View full text Add to dashboard Cite

The retinal protein proteorhodopsin is a homolog of the well-characterized light-driven proton pump bacteriorhodopsin. Basic mechanisms of proton transport seem to be conserved, but there are noticeable differences in the pH ranges of proton transport. Proton transport and protonation state of a carboxylic acid side chain, the primary proton acceptor, are correlated. In case of proteorhodopsin, the pK of the primary proton acceptor Asp-97 (pK ≈ 7.5) is unexpectedly close to environmental pH (pH ≈ 8). A significant fraction of proteorhodopsin is possibly inactive at natural pH, in contrast to bacteriorhodopsin. We investigated photoinduced kinetics of proteorhodopsin between pH 5 and pH 9 by time resolved UV/vis absorption spectroscopy. Kinetics is inhomogeneous within that pH region and can be considered as a superposition of two fractions. These fractions are correlated with the Asp-97 titration curve. Beside Asp-97, protonation equilibria of other groups influence kinetics, but the observations do not point toward major differences of primary proton acceptor function in proteorhodopsin and bacteriorhodopsin. The pK of proteorhodopsin and some of its variants is suspected to be an example of molecular adaptation to the physiology of the original organisms.

show abstract

“…(A similar experiment using various anion species (e.g., Br À , I À , NO 3 À ) might further support the above assignment. However, when the anions are changed, the photocycle of NpHR, the number of intermediates, and the decay rates of the intermediates should change (37)(38)(39), and the assignment may not be simple. We will investigate this point in the future.)…”

Section: Reaction Dynamics Of Nphr Monitored By the Tg Methodsmentioning

confidence: 99%

Reaction Dynamics of Halorhodopsin Studied by Time-Resolved Diffusion

Inoue

Kubo

Demura

et al. 2009

Biophysical Journal

View full text Add to dashboard Cite

Reaction dynamics of a chloride ion pump protein, halorhodopsin (HR), from Natronomonas pharaonis (N. pharaonis) (NpHR) was studied by the pulsed-laser-induced transient grating (TG) method. A detailed investigation of the TG signal revealed that there is a spectrally silent diffusion process besides the absorption-observable reaction dynamics. We interpreted these dynamics in terms of release, diffusion, and uptake of the Cl(-) ion. From a quantitative global analysis of the signals at various grating wavenumbers, it was concluded that the release of the Cl(-) ion is associated with the L2 --> (L2 (or N) <==> O) process, and uptake of Cl(-) occurs with the (L2 (or N) <==> O) -->NpHR' process. The diffusion coefficient of NpHR solubilized in a detergent did not change during the cyclic reaction. This result contrasts the behavior of many photosensor proteins and implies that the change in the H-bond network from intra- to intermolecular is not significant for the activity of this protein pump.

show abstract

Kinetic isotope effects in the photochemical reaction cycle of ion transporting retinal proteins

Cited by 7 publications

References 32 publications

Initial Reaction Dynamics of Proteorhodopsin Observed by Femtosecond Infrared and Visible Spectroscopy

Initial Reaction Dynamics of Proteorhodopsin Observed by Femtosecond Infrared and Visible Spectroscopy

Proteorhodopsin Photocycle Kinetics Between pH 5 and pH 9

Reaction Dynamics of Halorhodopsin Studied by Time-Resolved Diffusion

Contact Info

Product

Resources

About