Mechanism for the opsin shift of retinal's absorption in bacteriorhodopsin

Lugtenburg, J.; Muradin-Szweykowska, M.; Heeremans, C. E. M.; Pardoen, J. A.

doi:10.1021/ja00271a050

Cited by 97 publications

(35 citation statements)

References 2 publications

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“…This suggests that some mechanism other than alteration of charged amino acid perturbations is responsible for the additional opsin shift in the red cone pigment. Possibilities include changes in the hydrogen-bonding environment near the protonated Schiff base, changes in dipolar residues at other locations in the binding pocket (32), and proteininduced conformational changes of the retinal chromophore as observed in bacteriorhodopsin (7)(8)(9)(10)(11). Further Raman microprobe experiments on cone pigments should allow us to examine these possibilities.…”

Section: Discussionmentioning

confidence: 99%

Why are blue visual pigments blue? A resonance Raman microprobe study.

Loppnow

Barry

Mathies

1989

Proc. Natl. Acad. Sci. U.S.A.

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A resonance Raman microscope has been developed to study the structure of the retinal prosthetic group in the visual pigments ofindividual photoreceptor cells. Raman vibrational spectra are obtained by focusing the probe laser on intact photoreceptors frozen on a 77 K cold stage. To elucidate the mechanism of wavelength regulation in blue visual pigments, we have used this apparatus to study the structure of the chromophore in the 440-nm absorbing pigment found in

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Section: Discussionmentioning

confidence: 99%

Why are blue visual pigments blue? A resonance Raman microprobe study.

Loppnow

Barry

Mathies

1989

Proc. Natl. Acad. Sci. U.S.A.

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“…In particular, 13C and 1 5~ nmr spectra have yielded I important information in biological systems. Among these, two membrane proteins, rhodopsin (1) and bacteriorhodopsin (2)(3)(4)(5)(6), have been studied with a certain amount of success, using both nuclei as a probe for measuring the interactions of the I chromophore with the proteins. However, to be able to study pigments by nmr, they need first to be isolated from the I biological milieu by using different techniques, and the end ' results usually consist of a purified protein dispersed in a detergent or lyophilized to a thin film.…”

Section: Introductionmentioning

confidence: 99%

Protonation of a conjugated Schiff base by weak to strong acids: a ¹³C and ¹⁵N nuclear magnetic resonance study

Cossette¹,

Vocelle²

1987

Can. J. Chem.

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DANIEL COSSETTE and DANIEL VOCELLE. Can. J. Chem. 65, 661 (1987).The interactions (mostly protonation) between several carboxylic and mineral acids and trans,trans-2,4-heptadienylidene tert-butylamine (HBA) were determined by I3c and I5N nuclear magnetic resonance spectroscopies. Results indicate that protonation is only partial with weak acids in both polar and nonpolar solvents. No interaction between polar groups located on the acids and the polyenic chain of HBA seems to occur. The chemical shifts of all carbon atoms and also of the Schiff base nitrogen are linearly correlated with the acidity strength of the carboxylic acids.DANIEL COSSETTE et DANIEL VOCELLE. Can. J. Chem. 65, 661 (1987).Les interactions (surtout la protonation) entre plusieurs acides carboxyliques et minCraux avec la trans,trans-heptadiknylidkne-2,4 tert-butylamine (HBA) ont Ct C dCterminCes par la rCsonance magnCtique nuclCaire du I3C et du I5N. Les rCsultats indiquent que la protonation est partielle pour les acides faibles aussi bien pour les solvants polaires que non-polaires. Aucune interactionentre les groupes polaires des acides et la chaine polyCnique de HBA n'a pu &tre dCcelCe. Les dkplacements chimiques de tous les atomes de carbone et aussi de l'azote de la base de Schiff sont IinCairement correles avec la force de l'aciditk des acides carboxyliques.

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“…The essential point of this model is that cations affect the color transition only by changing the surface pH. The fact that deionization no longer has an effect on the spectrum of the purple membrane once the acidic lipids are removed or exchanged for neutral lipids gave strong evidence for this model (18) and its implication that metal cations are bound to the negatively charged surface of the purple membrane patch bR via nonspecific electrostatic attraction.Another model proposed by several other groups (21-32) emphasizes the existence of specific binding between some of the metal cations and negatively charged groups (e.g., carboxylate groups of Asp and Glu side chains) inside the protein, without excluding possible binding of some cations on the membrane surface (12,18,31). It was proposed (6,(22)(23)(24)32) that protonation changes near the Schiff base are directly linked to the binding of cations to the bR molecule.…”

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confidence: 99%

“…Removal of these cations from purple membrane patches (6,7) or acidification (2,8,9) causes a color transition from purple to blue. The absorption maximum of the retinal chromophore is believed to be primarily regulated by the electrostatic interactions between the charged or polar side chains of amino acids and the PSB, as well as certain carbon atoms along the retinal electronic system (10)(11)(12)(13)(14). From the structure (15) and genetic modification studies of bR (16,17), it has been found that Asp-85, Asp-212, and Arg-82 are charged groups in the retinal pocket.…”

mentioning

confidence: 99%

“…Another model proposed by several other groups (21-32) emphasizes the existence of specific binding between some of the metal cations and negatively charged groups (e.g., carboxylate groups of Asp and Glu side chains) inside the protein, without excluding possible binding of some cations on the membrane surface (12,18,31). It was proposed (6,(22)(23)(24)32) that protonation changes near the Schiff base are directly linked to the binding of cations to the bR molecule.…”

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confidence: 99%

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Effects of genetic replacements of charged and H-bonding residues in the retinal pocket on Ca2+ binding to deionized bacteriorhodopsin.

Zhang

El‐Sayed

Bonet

et al. 1993

Proc. Natl. Acad. Sci. U.S.A.

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Metal cations are known to be required for proton pumping by bacteriorhodopsin (bR). Previous studies found that bR has two high-affinity and four to six low-affinity Ca2+-binding sites. In our efforts to find the location of these Ca2+ sites, the effects of replacing charged (Asp-85, Asp-212, and Arg-82) and H-bonding (Tyr-185) residues in the retinal pocket on the color control and binding affinity of Ca2+ ions in Ca2+-regenerated bR were examined. The important results are as follows: (t) The removal of Ca2+ from recombinant bR in which charged residues were replaced by neutral ones shifted the retinal absorption to the blue, opposite to that observed in wild-type bR or in recombinant bR in which the H-bonding residue, Tyr-185, was replaced by a non-H-bonding amino acid (Phe). (h) Similar to the observation in wild-type bR, the binding of Ca2+ to the second site gave the observed color change in the recombinant bR samples in which charged residues were replaced by neutral ones. (ii) The residue replacements had no effect on the affinity constants of the four to six weakly bound Ca2+. (iv) The two high-affinity sites exhibited reduced affinity with substitutions; while the extent of the reduction depended on the specific substitution, each site was reduced by the same factor for each of the charged residue substitutions but by different factors for the mutant where Tyr-185 was replaced with Phe(Y185F). The above results suggest that the two Ca2+ ions in the two high-affinity sites are within interaction distance with one another and with the charged residues in the retinal pocket. The results further suggest that, while the interaction between Tyr-185 and the high-affinity Ca2+ ions is relatively short range and specific (with more coupling to the Ca2+ ion in the second affmity site), between the charged residues and Ca2+ ions it seems to be of the electrostatic (e.g., ion-ion) long range, nonspecific type. Although neither Asp-85, Asp-212, nor Arg-82 is individually directly involved in the binding of Ca2+ in these two sites, they might all participate in it. Together with the protonated Schiff base, the charged residues along with Tyr-185 and one or two Ca2+ ions (and probably a few water molecules) seem to form an electrostatically coupled system that is part of a cavity that controls the color and function of bR.Bacteriorhodopsin (bR) is the only protein in the purple membrane of Halobacterium halobium (1, 2). It contains a polypeptide chain of 248 amino acid residues (3), as well as a single retinylidene chromophore bound via a protonated Schiff base (PSB) to the E-NH2 group of Lys-216. Upon absorption of a photon, bR undergoes a photocycle (4) during which the all-trans to 13-cis isomerization of the chromophore takes place followed by the deprotonation of the PSB, and protons are pumped across the cell membrane. The resulting electrochemical proton gradient is then used by the bacteria for some metabolic processes (e.g., ATP synthesis) (4, 5).Well-washed purple membrane patches contain 3-4 mol o...

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Mechanism for the opsin shift of retinal's absorption in bacteriorhodopsin

Cited by 97 publications

References 2 publications

Why are blue visual pigments blue? A resonance Raman microprobe study.

Why are blue visual pigments blue? A resonance Raman microprobe study.

Protonation of a conjugated Schiff base by weak to strong acids: a ¹³C and ¹⁵N nuclear magnetic resonance study

Effects of genetic replacements of charged and H-bonding residues in the retinal pocket on Ca2+ binding to deionized bacteriorhodopsin.

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Mechanism for the opsin shift of retinal's absorption in bacteriorhodopsin

Cited by 97 publications

References 2 publications

Why are blue visual pigments blue? A resonance Raman microprobe study.

Why are blue visual pigments blue? A resonance Raman microprobe study.

Protonation of a conjugated Schiff base by weak to strong acids: a 13C and 15N nuclear magnetic resonance study

Effects of genetic replacements of charged and H-bonding residues in the retinal pocket on Ca2+ binding to deionized bacteriorhodopsin.

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Protonation of a conjugated Schiff base by weak to strong acids: a ¹³C and ¹⁵N nuclear magnetic resonance study