Dehydration-Induced Molecular Structural Changes of Purple Membrane of Halobacterium Halobium

Draheim, James E.; Gibson, Nicholas J.; Cassim, Joseph Y.

doi:10.1016/s0006-3495(88)83029-7

Cited by 15 publications

(34 citation statements)

References 34 publications

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“…Vacuum dehydrated films at p H 7 show effects ( Fig. 1) similar to those reported previously (Lazarev and Terpugov, 1980;Draheim et al, 1988). As the membrane is dehydrated, the absorbance maximum shifts to a lower wavelength, along with diminished extinction.…”

Section: Dehydration Transitionssupporting

confidence: 84%

“…After vacuum dehydration for 20 min at 13.33 Pa (0.1 torr), the absorbance maximum shifted to 528 nm. The dehydrated spectra are closer to those reported by Draheim et al (1988) than those of Lazarev and Terpugov (1980). Two isosbestic points were observed, one at 526 nm and the other at 640 nm.…”

Section: Dehydration Transitionssupporting

confidence: 74%

“…The purple chroniophore of bacteriorhodopsin is perturbed by dehydration, resulting in a blue-shifted absorbance maximum (Lazarev and Terpugov, 1980;Hildebrandt and Stockburger, 1984;Draheim et al, 1988). Recent spectroscopic (Hildebrandt and Stockburger, 1984;de Groot et al, 1989) and structural (Henderson et al, 1990;Papadopoulos et al, 1990) studies suggest the presence of water near the retinal Schiff base. The color changes occuring with dehydration may be caused by dissociation of water molecules specifically bound near the Schiff base.…”

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confidence: 99%

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Cooperativity of the Dehydration Blue‐shift of Bacteriorhodopsin*

Renthal¹,

Regalado²

1991

Photochem & Photobiology

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Dehydration of purple membrane (PM) causes a blue-shift of the absorbance maximum from 570 nm to about 530 nm [Lazarev and Terpugov (1980) Biochim. Biophps. Acta 590. 324-338;Hildebrandt and Stockburger (1984) Biochemistry 23,5539-55481. The absorbance spectra of PM dried in films at pH 0, 7 and 1 1 were measured at controlled relative humidities (RH). At pH 7, a blueshift was observed similar to that previously reported. At pH 0 (1 M H,SO,) a reversible transition was observed from the "acid blue membrane" (maximum near 600 nm at 100% R H ) to a blue-shifted dehydrated pigment (maximum near 578 nm at 50% RH). with isosbcstic points at 592 and 710 nm. At pH I 1 (NaOH) the absorbance maximum shifted to 530 nm. similar to the dehydrated form at pH 7. The fraction o f hydrated chromophore, X,,, was calculated (assuming only two chromophore states, hydrated and dehydrated) as a function of humidity and pH. The resulting curve at p H 7 showed a steep decline in X,, bclow 20'%, RH. Near this hydration level, water clusters on protein surfaces break up, causing side-chain pK reversals. The Hill coefficient for the transition was about 2, indicating the minimum number o f water molecules involved in a cooperative transition. The results suggest that as few as two water molccules are coordinated to the protonated retinal Schiff base of bacteriorhodopsin. A mechanism for the p H 7 dehydration blue-shift is proposed, involving a pK reversal of the protonated Schiff base and a nearby carboxyl side chain. At pH 0, a sharp decline in XI, occurs between 100 and 70% RH. Near this hydration level, complete protein surface coverage by a water monolaycr occurs. The Hill coefficient is about 20, suggesting involvement of a large region of the surlace. 1NTROI)UCTION

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Section: Dehydration Transitionssupporting

confidence: 84%

Section: Dehydration Transitionssupporting

confidence: 74%

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confidence: 99%

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Cooperativity of the Dehydration Blue‐shift of Bacteriorhodopsin*

Renthal¹,

Regalado²

1991

Photochem & Photobiology

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“…Removal of water from purple membrane alters various aspects of its function. Dehydration shifts the retinal absorbance maximum from 570 to 528 nm (3)(4)(5); inhibits the formation of the purple chromophore from bacterio-opsin and all-trans retinal (6); inhibits the irreversible step of the photocycle (the M1 → M2 transition) (7); inhibits the decay of photointermediate M † (8); and diminishes the crystallinity of the membrane at low pH (9). The effects of dehydration on purple membrane have provided insight into the proton pump mechanism in addition to offering a relatively simple example of spectral tuning in retinyl pigments.…”

Section: Introductionmentioning

confidence: 99%

Water and Carboxyl Group Environments in the Dehydration Blueshift of Bacteriorhodopsin¶

Renthal¹,

Gracia²,

Regalado³

2007

Photochemistry and Photobiology

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The proton channels of the bacteriorhodopsin (BR) proton pump contain bound water molecules. The channels connect the purple membrane surfaces with the protonated retinal Schiff base at the membrane center. Films of purple membrane equilibrated at low relative humidity display a shift of the 570 nm retinal absorbance maximum to 528 nm, with most of the change occurring below 15% relative humidity. Purple membrane films were dehydrated to defined humidities between about 50 and 4.5% and examined by Fourier transform infrared difference spectroscopy. In spectra of dehydrated‐minus‐hydrated purple membrane, troughs are observed at 3645 and 3550 cm−1, and peaks are observed at 3665 and 3500 cm−1. We attribute these changes to water dissociation from the proton uptake channel and the resulting changes in hydrogen bonding of water that remains bound. Also, in the carboxylic acid spectral region, a trough was observed at 1742 cm−1 and a peak at 1737 cm−1. The magnitude of the trough to peak difference between 1737 and 1742 cm−1 correlates linearly with the extent of the 528 nm pigment. This suggests that a carboxylic acid group or groups is undergoing a change in environment as a result of dehydration, and that this change is linked to the appearance of the 528 nm pigment. Dehydration difference spectra with BR mutants D96N and D115N show that the 1737–1742 cm−1 change is due to Asp 96 and Asp 115. A possible mechanism is suggested that links dissociation of water in the proton uptake channel to the environmental change at the Schiff base site.

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“…One favors the presence of water next to the Schiff base (2,(6)(7)(8)(9)(10), the other (27) rather promotes the excitonic model of Kriebel and Albrecht (1). Both models have advantages and drawbacks but neither one nor the other can rationalize all the physical and chemical properties of these pigments.…”

Section: Introduction Dicated That a Retinylidene Schiff Base In Nonpmentioning

confidence: 99%

Studies of the role of water on some imine–acid complexes by means of Raman spectroscopy

Turcotte¹,

Alex²,

Vocelle³

1992

Can. J. Chem.

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The percentages of protonation were determined for a conjugated Schiff base trans, trans-2,4-heptadienylidene tertbutylamine in the presence of 3-chloropropionic acid (CPR) and dichloroacetic acid (DCA) in three solvents of different polarities. In dioxane, a solvent of low polarity, protonation is only important for the strong acid DCA (50-60%). By using solvents of higher polarities, protonation is seen to increase and is almost complete for DCA in ethanol. When water molecules are added to these systems, hydrolysis of the Schiff base, measured inside the time span of the experiments (10 min), occurs readily in dioxane, is very slow in a chloroform-dioxane mixture (9: l), and is totally absent in a mixture of ethanol-dioxane (1 :9). Results indicate that water does not mediate protonation in all three sets of solvent combinations. The results are also discussed in terms of the possible role that water molecules could have in the visual and bacterial pigments. Les pourcentages de protonation ont CtC determines pour le cas d'une base de Schiff conjuguke, la trans,trans-2,4-heptadiknylidkne tert-butylamine, en presence de l'acide 3-chloropropionique (CPR) et de l'acide dichloroacCtique (DCA) dans trois solvants de differentes polarites. Dans le dioxane, un solvant de faible polaritk, la protonation n'est importante que pour l'acide fort DCA (50-60%). En utilisant des solvants de polarit6 plus klevke, la protonation augmente et est B peu pres complkte pour le DCA dans I'ethanol. Quand de l'eau est ajoutCe a ces systemes, l'hydrolyse de la base de Schiff, mesuree 21 l'intkrieur du temps d'enregistrement des spectres (10 min), est rapide dans le dioxane, est beaucoup plus lente dans un melange de chloroforme-dioxane (9: 1) et est totalement absente dans un melange d'kthanoldioxane (1 :9). Les resultats indiquent que l'eau ne favorise aucunement la protonation et cela vaut pour les trois ensem-I

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Dehydration-Induced Molecular Structural Changes of Purple Membrane of Halobacterium Halobium

Cited by 15 publications

References 34 publications

Cooperativity of the Dehydration Blue‐shift of Bacteriorhodopsin*

Cooperativity of the Dehydration Blue‐shift of Bacteriorhodopsin*

Water and Carboxyl Group Environments in the Dehydration Blueshift of Bacteriorhodopsin¶

Studies of the role of water on some imine–acid complexes by means of Raman spectroscopy

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