Properties of the catalytic (αβ)-core complex of chloroplast CF1-ATPase

Gromet-Elhanan, Zippora; Avital, Shlomo

doi:10.1016/0005-2728(92)90138-r

Cited by 19 publications

(9 citation statements)

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“…The hybrid MgATPase activity was fully sensitive to tentoxin, a specific CF 1 inhibitor (20), whereas the control or restored native RrF 0 F 1 ATP synthesis or hydrolysis activities were completely resistant to tentoxin (14,21). This result suggested that the ␤ subunit might be responsible for conferring tentoxin sensitivity to the F 1 enzyme.…”

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confidence: 60%

Hybrid Rhodospirillum rubrumF0F1 ATP Synthases Containing Spinach Chloroplast F1 β or α and β Subunits Reveal the Essential Role of the α Subunit in ATP Synthesis and Tentoxin Sensitivity

Tucker¹,

Du²,

Hein³

et al. 2000

Journal of Biological Chemistry

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Trace amounts (ϳ5%) of the chloroplast ␣ subunit were found to be absolutely required for effective restoration of catalytic function to LiCl-treated chromatophores of Rhodospirillum rubrum with the chloroplast ␤ subunit (Avital, S., and Gromet-Elhanan, Z. (1991) J. Biol. Chem. 266, 7067-7072). To clarify the role of the ␣ subunit in the rebinding of ␤, restoration of catalytic function, and conferral of sensitivity to the chloroplastspecific inhibitor tentoxin, LiCl-treated chromatophores were analyzed by immunoblotting before and after reconstitution with mixtures of R. rubrum and chloroplast ␣ and ␤ subunits. The treated chromatophores were found to have lost, in addition to most of their ␤ subunits, approximately a third of the ␣ subunits, and restoration of catalytic activity required rebinding of both subunits. The hybrid reconstituted with the R. rubrum ␣ and chloroplast ␤ subunits was active in ATP synthesis as well as hydrolysis, and both activities were completely resistant to tentoxin. In contrast, a hybrid reconstituted with both chloroplast ␣ and ␤ subunits restored only a MgATPase activity, which was fully inhibited by tentoxin. These results indicate that all three copies of the R. rubrum ␣ subunit are required for proton-coupled ATP synthesis, whereas for conferral of tentoxin sensitivity at least one copy of the chloroplast ␣ subunit is required together with the chloroplast ␤ subunit. The hybrid system was further used to examine the effects of amino acid substitution at position 83 of the ␤ subunit on sensitivity to tentoxin.The photosynthetic F 0 F 1 ATP synthases found in the thylakoids of chloroplasts and in the cytoplasmic membranes of photosynthetic bacteria couple the movement of protons down an electrochemical proton gradient to the synthesis of ATP during photophosphorylation. The general structure of these ATP synthases is highly conserved, consisting of F 0 , the membrane-spanning proton channel, and F 1 , the peripheral membrane sector, which contains the catalytic sites for reversible ATP synthesis. The F 0 is composed of four different subunits labeled a, b, bЈ, and c in photosynthetic bacteria (1) and I-IV in chloroplasts (2-4). The chloroplast F 0 subunits IV, I, II, and III are analogous to the bacterial a, b, bЈ, and c, respectively, with a probable stoichiometry of a 1 b 1 bЈ 1 c 9 -12 . F 1 from all sources is composed of five different subunits designated ␣ to ⑀ in order of decreasing molecular weight with a stoichiometry ofThe x-ray crystal structure of bovine heart mitochondrial F 1 (MF 1 ) 1 at 2.8-Å resolution (5) defined the three-dimensional structures of alternating ␣ and ␤ subunits as forming a closed hexamer having a portion of the ␥ subunit embedded in its central cavity. Among the nucleotide binding sites, which are located one at each of the six ␣/␤ interfaces, the three catalytic sites, located predominantly on ␤ subunits, were found to exist in three different conformational states. This asymmetric feature is compatible with the binding change mechanism, which...

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confidence: 60%

Hybrid Rhodospirillum rubrumF0F1 ATP Synthases Containing Spinach Chloroplast F1 β or α and β Subunits Reveal the Essential Role of the α Subunit in ATP Synthesis and Tentoxin Sensitivity

Tucker¹,

Du²,

Hein³

et al. 2000

Journal of Biological Chemistry

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“…4). One possible way to explain this would be if the binding of tentoxin causes a conformational change in the tentoxin-sensitive (3 …”

Section: Methodsmentioning

confidence: 99%

“…The incubation mixture for coupled refolding and reconstitution contained 0.2 pM of the purified chloroplast molecular chaperones, 0.087 ,uM of the denatured a subunit, 0.087 pM of the denatured (3 Proc. Natl.…”

Section: Methodsmentioning

confidence: 99%

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Chloroplast molecular chaperone-assisted refolding and reconstitution of an active multisubunit coupling factor CF1 core.

Chen

Jagendorf²

1994

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

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“…ATPase activity was assayed with 2 mM MgCI2 and 4 mM ATE The concentrations of added effectors were as for RrFt-cq/.31, and when stated low tentoxin, 1/~M and high tentoxin, 100/zM. CData modified from Gromet-Elhanan and Avital (1992) and Sokolov and Gromet-Elhanan (1995). ATPase activity was assayed as with RrFl, but with 1 mM azide, 40 mM octylglucoside and 20 mM sulfite.…”

Section: B 1 Soluble Atpase Activitiesmentioning

confidence: 99%

The photosynthetic F1-?3?3 and ?1?1 catalytic core complexes

Gromet-Elhanan

Sokolov

1995

Photosynth Res

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Minimal photosynthetic catalytic F1(αβ) core complexes, containing equimolar ratios of the α and β subunits, were isolated from membrane-bound spinach chloroplast CF1 and Rhodospirillum rubrum chromatophore RrF1. A CF1-α3β3 hexamer and RrF1-α1β1 dimer, which were purified from the respective F1(αβ) complexes, exhibit lower rates and different properties from their parent F1-ATPases. Most interesting is their complete resistance to inhibition by the general F1 inhibitor azide and the specific CF1 inhibitor tentoxin. These inhibitors were earlier reported to inhibit multisite, but not unisite, catalysis in all sensitive F1-ATPases and were therefore suggested to block catalytic site cooperativity. The absence of this typical property of all F1-ATPases in the α1β1 dimer is consistant with the view that the dimer contains only a single catalytic site. The α3β3 hexamer contains however all F1 catalytic sites. Therefore the observation that CF1-α3β3 can bind tentoxin and is stimulated by it suggests that the F1γ subunit, which is required for obtaining inhibition by tentoxin as well as azide, plays an important role in the cooperative interactions between the F1-catalytic sites.

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Properties of the catalytic (αβ)-core complex of chloroplast CF1-ATPase

Cited by 19 publications

References 44 publications

Hybrid Rhodospirillum rubrumF0F1 ATP Synthases Containing Spinach Chloroplast F1 β or α and β Subunits Reveal the Essential Role of the α Subunit in ATP Synthesis and Tentoxin Sensitivity

Hybrid Rhodospirillum rubrumF0F1 ATP Synthases Containing Spinach Chloroplast F1 β or α and β Subunits Reveal the Essential Role of the α Subunit in ATP Synthesis and Tentoxin Sensitivity

Chloroplast molecular chaperone-assisted refolding and reconstitution of an active multisubunit coupling factor CF1 core.

The photosynthetic F1-?3?3 and ?1?1 catalytic core complexes

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