Dependence of the proton translocation stoichiometry of cyanobacterial and chloroplast H+-ATP synthase on the membrane composition

Walraven, H.S. van; Scholts, M.J.C.; Koppenaal, F.; Bakels, R.H.A.; Krab, Klaas

doi:10.1016/0005-2728(90)90075-f

Cited by 30 publications

(9 citation statements)

References 38 publications

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“…It is to be stressed here that the use of the acidhase-transition technique excludes local proton gradients, which otherwise might explain this result. We have found similarly high values of H+/ATP for Synechococcus 6716 and chloroplast ATP synthases [38] reconstituted in liposomes prepared from cyanobacterial lipids. However, both for chloroplasts and for membrane vesicles from the Synechococcus enzyme, H+/ATP values close to 4 have been reported (see, for example, [38]).…”

Section: Thiol Modulation Of Spirulina Atp Synthasementioning

confidence: 60%

“…We have found similarly high values of H+/ATP for Synechococcus 6716 and chloroplast ATP synthases [38] reconstituted in liposomes prepared from cyanobacterial lipids. However, both for chloroplasts and for membrane vesicles from the Synechococcus enzyme, H+/ATP values close to 4 have been reported (see, for example, [38]). This has led us to postulate that the enzyme has the intrinsic ability to modulate this value.…”

Section: Thiol Modulation Of Spirulina Atp Synthasementioning

confidence: 60%

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On the activation mechanism of the H⁺‐ATP synthase and unusual thermodynamic properties in the alkalophilic cyanobacterium Spirulina platensis

Bakels

Walraven

Krab

et al. 1993

European Journal of Biochemistry

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The activation requirements and thermodynamic characteristics of ATP synthase from the alkalophilic cyanobacterium Spirulina platensis were studied in coupled membrane vesicles. Activation by methanol increased the V,,, while the K, for MgATP was unaffected (0.7 mM). We propose that in Sp. platensis, as in chloroplasts, the activating effect of methanol is based on perturbation of the y-E subunit interaction. Light-driven ATP synthesis by membrane vesicles of Sp. platensis was stimulated by dithiotreitol. The characteristics of the activation of the ATP synthase by the proton electrochemical potential difference ( A f i H + ) were analyzed on the basis of the uncoupled rates of ATP hydrolysis as a function of a previously applied proton gradient. Two values of AjiH+, at which 50% of the enzyme is active, were found; 13-14 kJ.mol-' for untreated membrane vesicles, and 4-8 kJ. mol-' for light-treated and dithiotreitol-treated membrane vesicles. These values are lower than the corresponding values for the oxidized and reduced forms, respectively, of the chloroplast enzyme. Although no bulk proton gradient could be observed, membrane vesicles of Sp. platensis were able to maintain an equilibrium phosphate potential (AG,) of 40-43.5 kJ.mol comparable to values found for Synechococcus 6716 and Anabaena 7120 membrane vesicles. Acidhase-transition experiments showed that the thermodynamic threshold, A,iiH+, for ATP synthesis, catalyzed by light-treated and dithiotreitol-treated Spirulina membrane vesicles, was less than 5 kJ. mol-' .The activation characteristics and the low thermodynamic threshold allow ATP synthesis to occur at low AjiH+ values. The findings are discussed, both with respect to differences and similarities with the enzymes from chloroplasts and other cyanobacteria, and with respect to the alkalophilic properties of Sp. platensis.The ATP synthase of cyanobacteria resembles that of chloroplasts in that the enzyme requires activation of synthesis or hydrolysis of ATP. All thylakoid membrane ATP synthases studied can be activated by the proton electrochemical potential differenct (A&+). In addition, the chloroplast ATP synthase is regulated by the redox state of the enzyme [l]. The magnitude of A,iiH+ required for activation of the ATP synthase is lowered upon reduction. Reduction of the enzyme involves the cleavage of a disulfide group in the y subunit and a concomitant displacement of the E subunit [2, 31. In vivo, the enzyme is reduced by thioredoxin which, in turn, is reduced by the photosynthetic electron flow from photosystem 1 through ferredoxin and a ferredoxin:thiore- Other in-vitro methods which induce activity of the chloroplast enzyme include treatment by heat, methanol, trypsin, detergents [8] and sulfite [9].It was shown earlier that ATP hydrolysis, catalyzed by the hydrophilic part of the ATP synthase (F,)

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Section: Thiol Modulation Of Spirulina Atp Synthasementioning

confidence: 60%

Section: Thiol Modulation Of Spirulina Atp Synthasementioning

confidence: 60%

On the activation mechanism of the H⁺‐ATP synthase and unusual thermodynamic properties in the alkalophilic cyanobacterium Spirulina platensis

Bakels

Walraven

Krab

et al. 1993

European Journal of Biochemistry

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“…5A) as well as from the value of A/~H+ imposed by a valinomycin-induced K ÷ diffusion potential where ATP hydrolysis was just inhibited (Fig. 5B) [19,27]. ATP synthesis in Synechocystis 6803 vesicles induced by acid-base transition essentially yields the same graph as Fig.…”

Section: From Equilibrium Between Apn+ and Phosphate Potentialmentioning

confidence: 64%

“…In the case of flux measurements in which an activation constraint as compared to thermodynamic measurements is not present also a H+/ATP of 3 dominates for oxidised chloroplasts Walraven et al [27] were used. A similar experiment is also given in Bakels et al [19].…”

Section: Comparison With Other Literaturementioning

confidence: 99%

The H⁺/ATP coupling ratio of the ATP synthase from thiol‐modulated chloroplasts and two cyanobacterial strains is four

et al. 1996

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In this paper the authors emphasise that the proton translocating ATP synthase from thiol-modulated chloroplasts and two cyanobaeterial strains has a coupling ratio of 4 protons per ATP synthesised or hydrolysed. This ratio is determined by several thermodynamic studies at equilibrium between phosphate potential (AGp) and proton gradient (zl/iu+), and is confirmed by measurement of proton flux during ATP hydrolysis. Ratios lower than 4 H+IATP that have been published in the past have predominantly been determined with the oxidised chloroplast enzyme. Errors in these measurements will be discussed.

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“…Reduction of the chloroplast F|F(,not only leads to lower activation energy for the enzyme bot also to an increase in HVATP, For the reduced enzyme H*/ATP values of between 4 and 5 have been obtained (Mills and Mitchell 1982), Similar values were given by Rumberg et al (1990). Since an increase in HVATP leads to a decrease in threshold A/iH+ for ATP synthesis also in this way the reduced enzyme can make ATP at lower level of A/(H+-For two cyanobacterial strains Synechococcus 6716 (van Walraven et al 1990, Bakels et al 1991 and Synechocystis 6803 it has been shown that the HVATP is 4, corresponding again to the reduced form of chioroplast FjF,j.…”

Section: Modulation Of the H*/atp Ratiomentioning

confidence: 79%

Function, structure and regulation of cyanobacterial and chloroplast ATP synthase

Walraven

Bakels

1996

Physiologia Plantarum

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The proton‐translocating ATP synthase from chloroplasts and cyanobacteria forms ATP upon photosynthetic electron transport by using the proton gradient across the thylakoid membrane. Both enzymes contain nine different subunits and from the similarity in gene organisation and the high degree of amino acid sequence homology of the subunits it appears that these ATP synthases might have a common ancestor. Both enzymes need to be activated by membrane energisation in order to perform catalytic activity but, in contrast to the chloroplast ATP synthase, that from the studied cyanobacteria (with the exception of Spirulina platensis) shows no effect of the redox state on activation. Functionally, the cyanobacterial enzyme corresponds to the reduced form of the chloroplast ATP synthase. In the chloroplast enzyme a stretch of 9 amino acids, including two cysteines in the γ‐subunit, is involved in this redox effect and this stretch is absent in cyanobacteria. With γ‐mutants from the cyanobacterium Synechocystis 6803 the role of this stretch is studied. When active, both the cyanobacterial and the reduced chloroplast ATP synthase transport 4 protons per ATP synthesised and hydrolysed. This ratio may depend on the environment of the enzyme such as protein and lipid composition and pH.

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Dependence of the proton translocation stoichiometry of cyanobacterial and chloroplast H+-ATP synthase on the membrane composition

Cited by 30 publications

References 38 publications

On the activation mechanism of the H⁺‐ATP synthase and unusual thermodynamic properties in the alkalophilic cyanobacterium Spirulina platensis

On the activation mechanism of the H⁺‐ATP synthase and unusual thermodynamic properties in the alkalophilic cyanobacterium Spirulina platensis

The H⁺/ATP coupling ratio of the ATP synthase from thiol‐modulated chloroplasts and two cyanobacterial strains is four

Function, structure and regulation of cyanobacterial and chloroplast ATP synthase

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Dependence of the proton translocation stoichiometry of cyanobacterial and chloroplast H+-ATP synthase on the membrane composition

Cited by 30 publications

References 38 publications

On the activation mechanism of the H+‐ATP synthase and unusual thermodynamic properties in the alkalophilic cyanobacterium Spirulina platensis

On the activation mechanism of the H+‐ATP synthase and unusual thermodynamic properties in the alkalophilic cyanobacterium Spirulina platensis

The H+/ATP coupling ratio of the ATP synthase from thiol‐modulated chloroplasts and two cyanobacterial strains is four

Function, structure and regulation of cyanobacterial and chloroplast ATP synthase

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On the activation mechanism of the H⁺‐ATP synthase and unusual thermodynamic properties in the alkalophilic cyanobacterium Spirulina platensis

On the activation mechanism of the H⁺‐ATP synthase and unusual thermodynamic properties in the alkalophilic cyanobacterium Spirulina platensis

The H⁺/ATP coupling ratio of the ATP synthase from thiol‐modulated chloroplasts and two cyanobacterial strains is four