ATPase of chloroplasts

CF, coupling factor 1, the hydrophilic portion of the proton-translocating ATPase of chloroplasts... 

G Beckers, RJ Berzborn and H Strotmann (1992) Zero-length crosslinking between subunits S and I of the H -translocating ATPase of chloroplasts. Biochim Biophys Acta 1101 97-104... 

A POSSIBLE MECHANISM FOR ATP SYNTHESIS AND ATP HYDROLYSIS BY THE FoF>j ATPase OF CHLOROPLASTS... 

Nelson N (1981) Proton-ATPase of chloroplasts, Curr. Top. Bioenerg. 11, 1-33. 

Nelson N (1981) Proton-ATPase of chloroplasts. In Current topics in bioenergetics, Sanadi DR and Vernon LP,eds. vol.ll, p. 1-33, Academic Press, New York... 

Blair, A., Ngo, L., Park, J., Paulsen, I. T. and Saier, M. H. Jr (1996). Phylogenetic analyses of the homologous transmembrane channel-forming proteins of the FoFi-ATPases of bacteria, chloroplasts and mitochondria, Microbiology, 142, 17-32. 

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)... 

Bottcher, B., Lucken, U., and Graber, P. (1995). The structure of the H+-ATPase from chloroplasts by electron cryomicroscopy. Biochem. Soc. Trans., 23, 780-5. 

Extensive studies have been carried out on the proton-translocating ATPase of mitochondrial, bacterial and chloroplast membranes. This enzyme can also function in reverse to exploit the electrochemical potential of protons built up by respiration for the synthesis of ATP from ADP and P .298 The synthesis of ATP can be effected by the application of external electrical pulses to the ATPase vesicles in suspension with submitochondrial particles, showing that the diffusion potential of the protons (ApH) is not used. The yield of ATP was linearly dependent on the number of pulses.299... 

An H+ electrochemical gradient (ApH+) provides the energy required for active transport of all classical neurotransmitters into synaptic vesicles. The Mg2+-dependent vacuolar-type H+-ATPase (V-ATPase) that produces this gradient resides on internal membranes of the secretory pathway, in particular endosomes and lysosomes (vacuole in yeast) as well as secretory vesicles (Figure 3). In terms of both structure and function, this pump resembles the F-type ATPases of bacteria, mitochondria and chloroplasts, and differs from the P-type ATPases expressed at the plasma membrane of mammalian cells (e.g., the Na+/K+-, gastric H+/K+-and muscle Ca2+-ATPases) (Forgac, 1989 Nelson, 1992). The vacuolar and F0F1... 

ATPase activity was also studied by Friebe et al. in 1997.17 They correlated the BOA and DIBOA effects on radicle elongation of Avena sativa seedlings with their effects on the activity of plasma membrane H+-ATPase from roots of Avena sativa cv. Jumbo and from Vida faba cv. Alfred. They hypothesized that an alteration in the plasma membrane ATPase activity could be the reason for an abnormal nutrient absorption in plants exposed to hydroxamic acids, because of the role that this enzyme plays in the ion gradient and, therefore, in the ionic transport through plasma membrane. The results of this experiment showed a strong inhibition in the activity of this enzyme in the plasma membrane of chloroplast and mitochondria when it was exposed to BOA and DIMBOA. This alteration implies early interactions with the assayed hydroxamic acids. 

The main argument in favour of this hypothesis is the presence in chloroplasts and mitochondria of DNA, which is different from the nuclear DNA and similar to the DNA of prokaryotes, as well as the similarity of chloroplast, mitochondrial and bacterial ribosomes and their significant difference from cytoplasmic ribosomes of eukaryotic cells. The chloroplasts and mitochondria were found to be close to bacterial cells in additional other biochemical features the presence in their membranes of phospholipid cardiolipin, which is absent in the plasma membrane of eukaryotes, and ATPases of one and the same type FiF0. 

Tricolorin A (46) and G (47) are prototype members of this class of amphiphilic glycoconjugates (24). They constitute the allelochemical principles of Ipomoea tricolor Cav., a plant used in traditional agriculture in Mexico as a cover crop to protect sugar cane against invasive weeds. Their molecular mechanism of action likely involves the inhibition of the FT-ATPase of the plasma membrane, an enzyme that plays a crucial role in plant cell physiology. Moreover, 46 acts as a natural uncoupler of photophosphorylation in spinach chloroplasts. This compound also displays general cytotoxicity against several... 

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). 

The latter process was shown to require ATP, but the source of this ATP was unclear and a matter of considerable dispute. The breakthrough came in 1954 when Arnon and his colleagues demonstrated light-induced ATP synthesis in isolated chloroplasts. The same year Frenkel described photophosphorylation in cell-free preparations from bacteria. Photophosphorylation in both chloroplasts and bacteria was found to be associated with membranes, in the former case with the thylakoid membrane and in the latter with structures derived from the plasma membrane, called chromatophores. In the following years work in a number of laboratories, including those of Arnon, Avron, Chance, Duysens, Hill, Jagendorf, Kamen, Kok, San Pietro, Trebst, Witt and others, resulted in the identification and characterization of various catalytic components of photosynthetic electron transport. Chloroplasts and bacteria were also shown to contain ATPases similar to the F,-ATPase of mitochondria. 

Fig. 7. Side view of the EcFo F, (left) and CFo F, (right) ATP synthases obtained by cryoelectron microscopy. See text for discussion. Figure source (A) Capaldi, Aggeler, Turina and Wilkens (1994) Coupling between catalytic sites and the proton channel in F F -type APTases. Trends in Biochem Sci 10 285 (B) Bottcher, LUcken and GrSber (1995) The structure of H -ATPase from chloroplasts by electron cryomicroscopy. Biochem Soc Trans 23 783. (B) is kindly provided by Dr. Peter Graber.

ML Richter, Z Gromet-Elhanan and R McCarty (1986) Reconstitution ofthe Ft ATPase of Rhodospirlllum rubrum by the P subunit of chloroplast coupling factor. J Biol Chem 261 12109-12113... 

EP Gogol, U Lcken and RA Capaldi (1987) The stalk connecting the F and Fq domains of ATP synthase visualized by electron microscopy of unstained specimens. FEBS Lett 219 274-278 B Bttcher, U Lcken and P Grber (1995) The structure of the H -ATPase from chloroplasts by electron... 

The Na K ATPase of the plasma membrane and the Ca " transporters of the sarcoplasmic and endoplasmic reticulums (the SERCA pumps) are examples of P-type ATPases they undergo reversible phosphorylation during their catalytic cycle and are inhibited by the phosphate analog vanadate. F-type ATPase proton pumps (ATP synthases) are central to energy-conserving mechanisms in mitochondria and chloroplasts. V-type ATPases produce gradients of protons across some intracellular membranes, including plant vacuolar membranes. 

Mitochondrial ATP synthase is an F-type ATPase (see Fig. 11-39 Table 11-3) similar in structure and mechanism to the ATP synthases of chloroplasts and eubac-teria. This large enzyme complex of the inner mitochondrial membrane catalyzes the formation of ATP from ADP and Pj, accompanied by the flow of protons from the P to the N side of the mem-... 

Mitochondrial ATP synthase of yeast contains at least 13 different kinds of subunits and that of ani-mals 16, twice as many as in E. coli. Subunits a, p, y, a, b, and c of the mitochondrial synthase correspond to those of E. coli. However, the mitochondrial homolog of E. coli 5 is called the oligomycin-sensitivity-conferring protein (OSCP). It makes the ATPase activity sensitive to oligomycin. The mitochondrial 8 subunit corresponds to e of E. coli or of chloroplasts. Mitochondrial e has no coimterpart in bacteria. ... 

The five polypeptides of chloroplast coupling factor one (CFi) have a subunit stoichiometry of 3a, 3p, Y, 5, e designated in order of decreasing molecular weight (1-3). Nucleotide binding and ATPsynthase/ATPase activity have been associated with the p subunit per CFi and evidence suggests that the three active sites are functionally linked (4). Purified CFi is a latent ATPase which can be activated to show specificity for Mg (5-8) or Ca (9-12). 

The ATPase complex of chloroplasts (H -ATPase, ATP-synthase) carries out synthesis (hydrolysis) of ATP coupled with transmembrane transport of hydrogen ions. This complex consists of a hydrophylic catalytic part called coupling factor CF, and a hydrophobic part, CFq, the function of which is to translocate protons towards CF. CFj can bind as many as six nucleotide molecules / /. After CF precipitation by ammonium sulfate with subsequent gel filtration, the enzyme retains about 1 mol of tightly bound nucleotides consisting mainly of ADP /2/. 

In the FoFi-ATPase of mammalian and yeast mitochondria, the oligomy-cin sensitivity conferring protein (OSCP) is one of the subunits of the enzyme complex, and is needed for inhibition of ATP hydrolysis by oligomycin (1). The amino acid sequence of OSCP from beef heart mitochondria is homologous to the amino acid sequence of the S-subunit of the Fi-ATPase from E. coli, 26.4% (2), chloroplasts, 25.3% (3), and Rhodospirill urn rubrum, 28.9% (2). However, only R. rubrum is sensitive to oligomycin (4). It has also been shown that R. rubrum Fj-ATPase, with the B-subunits substituted with B from E. coli, is not oligomycin sensitive when reconstituted to depleted membranes (5). 

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