Phosphorus-31 NMR study of the interaction of cations with purple membrane and of the purple-blue transition

Roux, Michel; Seigneuret, Michel; Rigaud, Jean‐Louis

doi:10.1021/bi00418a051

Cited by 13 publications

(16 citation statements)

References 35 publications

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“…31 P NMR results 34 show significant perturbation of the phosphorous NMR signal which starts at a cation to bR ratio of 2:1 for titration with Nd 3+ , i.e., after saturating the two high-affinity protein-binding sites. 31 P NMR results 34 show significant perturbation of the phosphorous NMR signal which starts at a cation to bR ratio of 2:1 for titration with Nd 3+ , i.e., after saturating the two high-affinity protein-binding sites.…”

Section: Resultsmentioning

confidence: 98%

Calcium and Magnesium Binding in Native and Structurally Perturbed Purple Membrane

Griffiths¹,

King²,

Yang³

et al. 1996

J. Phys. Chem.

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The number and identity of the metal cations bound to wild-type bacteriorhodopsin (bR) are determined by using inductively coupled plasma mass spectrometry (ICP-MS) and ICP emission techniques. The results indicate that there at ≈2 total Ca 2+ and Mg 2+ per bR molecule with a ratio of ≈3:1 Ca 2+ to Mg 2+ . This observed ratio is found to agree with the calculated ratio using previously determined binding constants for the two high affinity sites of Ca 2+ to deionized bR et al. Biophys. J. 1992 et al. Biophys. J. , 61, 1201. This suggests that the high-affinity binding sites in deionized bR are similar to those in native bR. Structural perturbation of the native membrane by cleavage of the C-terminus decreases the number of ions per bR to 1.4. The observed ratio of total ions in this sample to total ions in bR is found to agree with that calculated using known binding constants for each. The results on the number of metal cations/bR and their ratio in bacterioopsin agrees with the calculated number using previously observed binding constants in deionized bO (Yang; et al. Biophys J., in press) only if one assumes that the second high-affinity site (not the first) is removed by retinal removal. Removal of 75% of the lipids from the purple membrane is found to greatly reduce the number of metal cations from 2 to 0.16. This suggest that if metal cations are in the two high-affinity sites (which are the only type of binding sites evident in our native bR sample), the removal of lipids, known to change the protein tertiary structure, changes also the metal ion binding sites.X

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Section: Resultsmentioning

confidence: 98%

Calcium and Magnesium Binding in Native and Structurally Perturbed Purple Membrane

Griffiths¹,

King²,

Yang³

et al. 1996

J. Phys. Chem.

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“…Even then, the divalent cation concentration had to be greater than 40 mM to see an effect. Roux et al (1988) suggested that lipids may have a role in cation binding; they used 31P-NMR to show that the binding of divalent cations resulted in an increased chemical shift anisotropy of the phosphates. Similar results are seen at increased pH due to phosphate ionization.…”

Section: Lipid Effectsmentioning

confidence: 99%

PURPLE MEMBRANE: SURFACE CHARGE DENSITY and THE MULTIPLE EFFECT OF pH and CATIONS

Jonas

Koutalos

1990

Photochem & Photobiology

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“…It has recently been reported that deionized blue membrane could be converted into "deionized purple membrane" by NaOH titration with an apparent pK of 5.4, and the authors argued that the purple membrane at pH >6.0 was still effectively deionized because the amount of Na+ required to induce the color change in NaOH titration was an order of magnitude less than the NaCl required for titration of a blue membrane at the same initial pH (31,32). The same argument was also used by other authors to separate pH and Na+ effects (33).…”

Section: Titration Of Blue Membrane With Basementioning

confidence: 99%

Surface pH controls purple-to-blue transition of bacteriorhodopsin. A theoretical model of purple membrane surface

Szundi

Stoeckenius

1989

Biophysical Journal

114

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We have developed a surface model of purple membrane and applied it in an analysis of the purple-to-blue color change of bacteriorhodopsin which is induced by acidification or deionization. The model is based on dissociation and double layer theory and the known membrane structure. We calculated surface pH, ion concentrations, charge density, and potential as a function of bulk pH and concentration of mono- and divalent cations. At low salt concentrations, the surface pH is significantly lower than the bulk pH and it becomes independent of bulk pH in the deionized membrane suspension. Using an experimental acid titration curve for neutral, lipid-depleted membrane, we converted surface pH into absorption values. The calculated bacteriohodopsin color changes for acidification of purple, and titrations of deionized blue membrane with cations or base agree well with experimental results. No chemical binding is required to reproduce the experimental curves. Surface charge and potential changes in acid, base and cation titrations are calculated and their relation to the color change is discussed. Consistent with structural data, 10 primary phosphate and two basic surface groups per bacteriorhodopsin are sufficient to obtain good agreement between all calculated and experimental curves. The results provide a theoretical basis for our earlier conclusion that the purple-to-blue transition must be attributed to surface phenomena and not to cation binding at specific sites in the protein.

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Phosphorus-31 NMR study of the interaction of cations with purple membrane and of the purple-blue transition

Cited by 13 publications

References 35 publications

Calcium and Magnesium Binding in Native and Structurally Perturbed Purple Membrane

Calcium and Magnesium Binding in Native and Structurally Perturbed Purple Membrane

PURPLE MEMBRANE: SURFACE CHARGE DENSITY and THE MULTIPLE EFFECT OF pH and CATIONS

Surface pH controls purple-to-blue transition of bacteriorhodopsin. A theoretical model of purple membrane surface

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