Pump and displacement currents of reconstituted ATP synthase on black lipid membranes

Christensen, B.; Gutweiler, M.; Grell, Ernst; Wagner, Norbert; Pabst, Rainer; Dose, Klaus; Bamberg, Ernst

doi:10.1007/bf01870929

Cited by 7 publications

(3 citation statements)

References 43 publications

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“…Because in F o F 1 -ATPase hydrolysis and synthesis of ATP are associated with ion translocation in the membrane-embedded F o part, an electrical signal is expected after activation of the enzyme with ATP or ADP 1 P i . This has been demonstrated previously using the F o F 1 -ATPase from Rhodospirillum rubrum (Christensen et al, 1988). Activation was accomplished with a photolytic ATP-or ADP-concentration jump using caged ATP and caged ADP, respectively.…”

Section: Introductionmentioning

confidence: 78%

Charge Displacements during ATP-Hydrolysis and Synthesis of the Na+-Transporting FoF1-ATPase of Ilyobacter tartaricus

Burzik

Kaim

Dimroth

et al. 2003

Biophysical Journal

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Transient electrical currents generated by the Na(+)-transporting F(o)F(1)-ATPase of Ilyobacter tartaricus were observed in the hydrolytic and synthetic mode of the enzyme. Two techniques were applied: a photochemical ATP concentration jump on a planar lipid membrane and a rapid solution exchange on a solid supported membrane. We have identified an electrogenic reaction in the reaction cycle of the F(o)F(1)-ATPase that is related to the translocation of the cation through the membrane bound F(o) subcomplex of the ATPase. In addition, we have determined rate constants for the process: For ATP hydrolysis this reaction has a rate constant of 15-30 s(-1) if H(+) is transported and 30-60 s(-1) if Na(+) is transported. For ATP synthesis the rate constant is 50-70 s(-1).

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Section: Introductionmentioning

confidence: 78%

Charge Displacements during ATP-Hydrolysis and Synthesis of the Na+-Transporting FoF1-ATPase of Ilyobacter tartaricus

Burzik

Kaim

Dimroth

et al. 2003

Biophysical Journal

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“…It was used because of its blue/UV light insensitivity. The usual protonophores like carbonylcyanide p-trifluoromethoxyphenylhydrazone and Tetrachloro-2-trifluoromethylbenzimidazole show electric artifacts on the planar lipid films caused by blue light absorption (26). All chemicals were analytical grade and were purchased from local distributors.…”

Section: Methodsmentioning

confidence: 99%

Light-driven proton or chloride pumping by halorhodopsin.

Bamberg

Tittor

Oesterhelt

1993

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

119

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Halorhodopsin from Halobaceriwn halobium was purified and reconstituted with lipids from purple membranes. The resulting protein-containing membrane sheets were adsorbed to a planar lipid membrane and photoelectric properties were analyzed. Depending on light conditions, halorhodopsin acted either as a light-driven chloride pump or as a proton pump: green light caused chloride transport and additional blue light induced proton pumping. In the living cell, both of these vectorial processes would be directed toward the cytoplasm and, compared to ion transport by bacteriorhodopsin, this is an inversed proton flow. Azide, a catalyst for reversible deprotonation of halorhodopsin, enhanced proton transport, and the deprotonated Schiff base in the 13-cis configuration (11410) was identified as the key intermediate of this alternative catalytic cycle in halorhodopsin. While chloride transport in halorhodopsin is mediated by a one-photon process, proton transport requires the absorption of two photons: one photon for formation of H410 and release of a proton, and one photon for photoisomerization of H410 and re-formation of H578 with concomitant uptake of a proton by the Schiff base.The retinal protein halorhodopsin occurs in the cell membrane of Halobacterium halobium in addition to the proton pump bacteriorhodopsin (for review, see ref. 1). Its function was identified as that ofan inwardly directed Cl-pump (2, 3). After photoisomerization of all-trans-retinal to the 13-cis isomer, halorhodopsin passes a series of distinct intermediates characterized by their respective absorption maxima before returning to the initial state within =14 ms (4). No reversible deprotonation of the Schiff base is connected with the Cl-transport cycle. However, halorhodopsin can produce in a side reaction a species called H410. This product is produced from the photocycle intermediate H520 and contains a deprotonated Schiff base in the 13-cis configuration (5) (see Fig. 7). From the H410 state halorhodopsin returns in a thermal reaction in the time range of seconds to the initial state. Thus, continuous green light inhibits Cl-pumping under concomitant accumulation of H410 (6). Photochemically, the H410 state after isomerization returns much faster to the initial state, and this phenomenon causes the observed blue light regulation of halorhodopsin activity. Thus, irradiance with white light (blue and green light) resulted in an optimal Cl--dependent stationary photocurrent in black lipid membrane experiments (6).Azide accelerates accumulation of H410 drastically, and this was seen as an accelerated inhibition of Cl-transport in green light and a fast reactivation by additional blue light. The effect ofazide is catalysis of the deprotonation reaction of the Schiff base (7,8). Recent elucidation of the proton transport mechanism in bacteriorhodopsin by structural, genetic, biochemical, and biophysical studies (9, 10) helped considerably in understanding the analogue molecular processes in halorhodopsin. Halorhodopsin lacks the aspartic...

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“…Most systems can be synchronized by light-flash excitation in an indirect way by the lightinduced release of protons (Gutman, 1986) and ATP (Christensen et al, 1988), Ca, etc., from caged substances. Several systems can be excited with electric pulses (as in the case of neurons).…”

Section: Introductionmentioning

confidence: 99%