ATPase chloroplast

Kometani etal.(93) used a theory for energy transfer from a donor to acceptors in a plane to determine the location of the retinal chromophore relative to the membrane surface. Another similar study on the location of the active site of chloroplast ATPase relative to the membrane surface has also been carried out.(94)... 

B. A. Baird, U. Pick, and G. G. Hammes, Structural investigation of reconstituted chloroplast ATPase with fluorescence measurements, J. Biol. Ckem. 254, 3818-3825 (1979). 

Transporting ATP synthase [EC 3.6.1.34] in plants, also referred to as chloroplast ATPase and CFiCFo-ATPase, catalyzes the hydrolysis of ATP to produce ADP and orthophosphate. When coupled with proton transport the reverse reaction results in the synthesis of ATP by this multisubunit complex. CFi, isolated from the rest of the membrane-bound complex, retains the ATPase activity but not the proton-translocating activity. 

The digitonin preparation of PSI-RC has also been demonstrated to be able to catalyze a light-induced proton uptake when incorporated in phospholipid liposomes and illuminated in the presence of ascorbate and phenazine methosulphate [47] incorporation of chloroplast ATPase in the same system yielded the reconstitution of photophosphorylation in a model system. The PSI-RC preparation therefore seems to possess all the functional features of PSI for the vectorial transmembrane electron transfer [48] (see Fig. 4.7). 

Use of a high field to activate a membrane enzyme was first reported by Witt et al. (25) in 1976. They used dc pulses of approximately 1 kV/cm and of 1-ms duration to induce ATP synthesis by the chloroplast ATPase. Following this initial work, there have been many reports on 1-kV/ cm dc field-induced ATP synthesis in different ATP synthetic systems (see the literature cited in references 13 and 14). The main conclusion from these studies is that an applied field-induced transmembrane potential can facilitate ATP release from the enzyme whether a PEF can affect enzyme turnover is not clear. Because 1-kV/ cm dc fields also cause severe Joule heating of a sample suspension, thermal effects cannot be easily avoided except when very short electric pulses (microseconds) are used. Thus, the method has limited utility for electroactivation experiments. The PEF method is, however, quite popular for the study of electroporation and electrofusion of cell membranes (see the chapter by J. Weaver in this volume), electroinsertion of membrane proteins (26), and electrotransfection of cells (27). 

CHARACTERIZATION OF NUCLEOTIDE BINDING SITES ON ISOLATED CHLOROPLAST ATPase BY MODIFICATION WITH 7-CHLORO-4-NITRO-BENZOFURAZAN... 

The observed single channel currents were carried by H through the isolated and reconstituted chloroplast ATPase. We demonstrate that it is the intact enzyme complex CFqCF] and not the membrane sector CFq alone that constitutes a voltagegated, proton selective channel with a hi unit conductance of 1-5 pS at pH 53-pH 8.0. The open probability P of the CFqCFj channel increased considerably with increasing membrane voltage (from Pq < 1% (V < 120 mV) to Pq < 30% (120 mV < V 200 mV)). In the presence of ADP (3 jxM) and Pj (5 jiM), wich specifically bind to CF the open probability decreased and venturiddin (1 i,M), a specific inhibitor of H flow through GFq in thylakoid membranes, blocked the chaimel almost completely. 

FIGURE 1 Reaction scheme for ATP synthesis and hydrolysis by membrane- bound chloroplast ATPase... 

DOES THE CHLOROPLAST ATPase HAVE A VARIABLE AFFINITY FOR ADP ... 

Characterization of Nucleotide Binding Sites on Isolated Chloroplast ATPase by Modification with 7-Chloro-4-Nitro-Benzofurazan 77... 

Does the Chloroplast ATPase have a Variable Affinity for ADP 153... 

Nechushtai R, Muster P,Binder A, Liveanu V and Nelson N (1983) Photosystem I reaction center from the thermophilic cyanobacterium mastigocladus laminosus, Proc. Natl. Acad. Sci. USA 80, 1179-1183. Nelson N (1983) Structure and synthesis of chloroplast ATPase, Methods Enzymol. 97 510-523. 

The chloroplast ATPase is known to be in an inactive state in the dark. 

The specific activities of the complex decline after reconstitution, as can be seen from Table 1. In the presence of an uncoupler a strong stimulation is observed, which indicates an efficient incorporation of the ATPase complex and a relatively low leakiness for protons. Thus, the ATPase proteoliposomes prepared from natural lipids function well at 50°C, the optimal growth temperature of SyneohooooQUS 6716. The specific hydrolysis and exchange activities are similar to those, found for reconstituted chloroplast ATPase (Pick, Racke2 1979). ... 

Shahak Y, Admon A and Avron M (1982) Transmembrane electrical potential formation by chloroplast ATPase complex (CFj -CFq) proteoliposomes, FEBS Lett. 150, 27-31. 

FUNCTIONAL PROPOERTIES OF CHLOROPLAST ATPase THE FATE OF TIGHTLY BOUND ADP AND ATP IN ILLUMINATED CHLOROPLASTS... 

At least two types of bound adenine nucleotides are known that participate in the reactions of chloroplast ATPase, the nucleotides which bind to the catalytic site and those which are defined as "tightly bound" nucleotides. 

Bar-Zvi D and Shavit N (1982) Modulation of the chloroplast ATPase by tight binding of nucleotides. Biochim. Biophys. Acta 681, 451-458. Bickel-Sandkotter S (1983) Loose and tight binding of adenine nucleotides by membrane-associated chloroplast ATPase. Biochim. Bioophys. Acta 723, 71-77. 

Graber P, Schlodder E and Witt HT (1977) Conformational change of the chloroplast ATPase induced by a transmembrane electric field and its correlation to phosphorylation. Biochim. Biophys. Acta 461, 426-440. 

Schlodder E and Witt HT (1981) Relation between the initial kinetics of ATP synthesis and of conformational changes in the chloroplast ATPase studied by external field pulses. Biochim. Biophys. Acta 635, 571-584. Schumann J and Strotmann H (1981) The mechanism of induction and deactivation of light-triggered ATPase, In Photosynthesis II. Electron Transport and Photophosphorylation, (ed. G Akoyunoglou) pp. 881-892. Balaban, Philadelphia... 

Bar-Zvi D and Shavit N (1982a) Modulation of the chloroplast ATPase by tight binding of nucleotides. Biochim. Biophys. Acta 681, 451-58. 

A DUAL pH OPTIMUM MODEL FOR ACTIVATION OF THE CHLOROPLAST ATPase, CF -CF,... 

Mills JD and Mitchell P (1982) Thiol modulation of CF -CFj stimulates acid/ base-dependent phosphorylation by pea chloroplasts, FEBS Letters 144,63-67. Mills JD and Mitchell P (1983) Thiol modulation of the chloroplast ATPase and its effect on photophosphorylation, Biochim. Biophys. Acta, in press. Mitchell P (1981) Biochemical mechanism of protonmotivated phosphorylation in Fq-Fj ATPase molecules. In Lee CP et al, eds. Mitochondria and microsomes, pp 427-457. Boston,Mass Addison-Wesley. 

Wagenvoord RJ, Yerschoor GJ and Kem p A (198I) Photolabeling with 8-azido adenine nucleotides of adenine nucleotide-binding sites in isolated spinach chloroplast ATPase (CF ), Biochim. Biophys. Acta 634, 229-236. Williams N and Coleman PS (1982) Exploring the adenine nucleotide binding sites with a new photoaffinity probe, 3 -0-(4-benzoyl)benzoyl adenosine 5 -triphosphate, J. Biol. Chem. 257, 2834-2841. 

LOOSE AND TIGHT BINDING OF ADENINE NUCLEOTIDES BY MEMBRANE ASSOCIATED CHLOROPLAST ATPase... 

Schlodder E and Witt HT (1981) Relation between the initial kinetics of ATP synthesis and of conformational changes in the chloroplast ATPase studied by external field pulses. Biochim. Biophys. Acta 635, 571-584... 

ACTIVATION OF THE LIGHT TRIGGERED CHLOROPLAST ATPase AN INHIBITORY PEPTIDE... 

Roos P, Berzborn RJ (1983) Electroimmunodiffusion- a-powerful tool for quantitative determinations of both soluble and membrane bound chloroplast ATPase CF. Z.f. Naturforsch. in press... 

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