Energy coupling in an ion pump

Kataoka, Mikio; Kamikubo, Hironari; Tokunagga, Fumio; Brown, Leonid S.; Yamazaki, Yoichi; Maeda, Akio; Sheves, Mordechai; Needleman, Richard; Lanyi, Janos Κ.

doi:10.1016/0022-2836(94)90037-x

Cited by 140 publications

(130 citation statements)

References 54 publications

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“…The second observation, made from x-ray diffraction, was that deprotonation of the Schiff base of the D85N mutant by raising the pH in the dark caused the protein to assume an equilibrium mixture of conformations that exhibit structural changes seen otherwise only in the M photointermediate (29). In the D85N/ D96N double mutant the equilibrium contained a large amount of the M-like conformation even with the Schiff base protonated.…”

Section: Partial Reactions Of the Photocycle Observed Without Illuminmentioning

confidence: 99%

Mechanism of Ion Transport across Membranes

Lanyi

1997

Journal of Biological Chemistry

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192

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Section: Partial Reactions Of the Photocycle Observed Without Illuminmentioning

confidence: 99%

Mechanism of Ion Transport across Membranes

Lanyi

1997

Journal of Biological Chemistry

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192

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“…In the light-driven proton pump, bacteriorhodopsin, such a conformational shift seems to be related to the change of the access of the buried proton binding group, the retinal Schiff base, from the extracellular to the cytoplasmic membrane surface (2)(3)(4). A mechanism based on such a two-state conformational change, and in particular on an alternating access of a single binding site, must account for transport in some of the more complex ion pumps also (5).…”

mentioning

confidence: 99%

A local electrostatic change is the cause of the large-scale protein conformation shift in bacteriorhodopsin

Brown

Kamikubo

Zimányi

et al. 1997

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

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During light-driven proton transport bacteriorhodopsin shuttles between two protein conformations. A large-scale structural change similar to that in the photochemical cycle is produced in the D85N mutant upon raising the pH, even without illumination. We report here that (i) the pK a values for the change in crystallographic parameters and for deprotonation of the retinal Schiff base are the same, (ii) the retinal isomeric configuration is nearly unaffected by the protein conformation, and (iii) preventing rotation of the C 13 OC 14 double bond by replacing the retinal with an all-trans locked analogue makes little difference to the Schiff base pK a . We conclude that the direct cause of the conformational shift is destabilization of the structure upon loss of interaction of the positively charged Schiff base with anionic residues that form its counter-ion.

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“…In Mope,~ a cleft permeable for water molecules as well as for small weak acids (azide) is formed in the cytosolfacing part of bR [10,14,21]. In the wild-type bacteriorhodopsin, the appearance of water near Asp-96 leads to a decrease a its pK [22][23][24][25]. In the D96N mutant, azide penetrates :hrough this cleft and protonates the Schiff base [14,20].…”

Section: Resultsmentioning

confidence: 99%

Complicated character of the M decay pH dependence in the D96N mutant is due to the two pathways of the M conversion

1996

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~bstract At high ionic strength, the pH dependence of the M intermediate decay in a photocycle of the D96N mutant bacteriorhodopsin shows a complicated behavior which is found lo be due to the coexistence of two pathways of the M conversion. The M decay which dominates at pH < 5 is coupled to the proton uptake from the cytoplasmic surface and proceeds probably through the N intermediate. This pathway is inhibited by glutaraldehyde, the potent inhibitor of M decay in the wildtype bacteriorhodopsin and of the azide-facilitated M decay in the D96N mutant. Another pathway of the M decay is predominant at pH > 5. This pathway is insensitive to glutaraldehyde and some other similar inhibitors (lutetium ions, sucrose and glycerol). On the other hand, it is sensitive to the pK changes ,ff the group X (Glu-204) in the outward proton pathway. Possibly, the M decay through this pathway represents a reverse H + transport process (the proton uptake from the external surface) and proceeds via the L intermediate.

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Energy coupling in an ion pump

Cited by 140 publications

References 54 publications

Mechanism of Ion Transport across Membranes

Mechanism of Ion Transport across Membranes

A local electrostatic change is the cause of the large-scale protein conformation shift in bacteriorhodopsin

Complicated character of the M decay pH dependence in the D96N mutant is due to the two pathways of the M conversion

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