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1980 (1)
1Author    G. Ünther, F. E. SchererRequires cookie*
 Title    A New M ethod to Prepare M em brane F ractions Containing Ionophore-Stim ulated A T P a se from Pumpkin H ypocotyls (Cucurbita maxima, L .)  
 Abstract    In membrane fractions from pumpkin hypocotyls AT­ Pase activity was stimulated by a combination o f CCCP (carbonyl cyanide m-chlorophenylhydrazone), a pro-tonophore, and valinomycin, a K +-ionophore. Singly, these ionophores stimulated ATPase activity much less. Nigericin, an H+/K +-antiporter, and nystatin, a cation pore, had similar effects as the combination o f CCCP and valinomycin. The results suggest the presence o f a cation-translocating ATPase which is stimulated by ionophores by dissipating cation gradients formed in the vesicles. A major part of the ionophore-stimulated ATPase activity correlat­ ed with marker enzymes for plasma membranes but part o f it could be located in other compartments. 
  Reference    Z. Naturforsch. 37c, 550 (1982); received March 5 1982 
  Published    1982 
  Keywords    H +-ATPase, Ionophores, Plasma Membrane, Cucurbita 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0550_n.pdf 
 Identifier    ZNC-1982-37c-0550_n 
 Volume    37 
2Author    Achim Hager, Roland Frenzel, D. Orothee LaibleRequires cookie*
 Title    ATP-dependent Proton Transport into Vesicles of Microsomal Membranes of Zea mays Coleoptiles  
 Abstract    ATP-dependent proton pumps were found in the vesicles of microsomal membrane fractions of maize coleoptiles. Two membrane fractions isolated by density gradient centrifugation were identified by the aid of marker enzymes and electron microscopic analysis. Membrane fraction A largely consisted of vesicles of smooth ER and of the Golgi complex, fraction B predominantly of vesicles of plasmalemma and rough ER. The pH-indicator, neutral red, was used to measure changes in pH in the vesicles after ATP addition. Due to the binding of protonated neutral red molecules (NRH+) to negative charges of the energized membrane, a strong metachromasy of NRH+-absorption can be observed. Therefore, in order to accurately measure A pH a pH-dependent change in absorption of neutral red covering the whole NR-spectrum was set up as difference spectra. The commonly employed method of measuring AA of neutral red at just one wavelength (525 nm) leads to entirely incorrect results. It could be demonstrated that the ATP-dependent translocation of H+-ions into the interior of the vesicles was most efficient at pH 7. Acidification, which reaches its maximum 10-15 min after ATP addition, can be reverted by adding CCCP. An ATP-dependent proton-translocation into the vesicles of fraction B was also observed, however, the proton translocation is less than that found in fraction A in relation to the amount of protein found in each. The membrane fraction A displays a strong oxidation of NADH subsequently followed by an alkalization of the medium. This process cannot be reverted by adding CCCP. NADH oxidation at membranes of fraction A is consequently not an integral part of a redox-pump. A possible significance of the ATP-dependent proton pump in membranes of the ER and Golgi fraction of coleoptiles is discussed in connection with auxin induced elongation growth. 
  Reference    Z. Naturforsch. 35c, 783—793 (1980); received May 22 1980 
  Published    1980 
  Keywords    Proton Pump, H+-ATPase, Zea mays, Coleoptile, Auxin 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0783.pdf 
 Identifier    ZNC-1980-35c-0783 
 Volume    35 
3Author    A. Hager, M. H. Elm LeRequires cookie*
 Title    Properties of an ATP-Fueled, Cl~-Dependent Proton Pump Localized in Membranes of Microsomal Vesicles from Maize Coleoptiles  
 Abstract    Vesicles prepared from the microsomal membrane fraction of maize coleoptiles possess an ATP-fueled H +-transport into the vesicles. It is highly possible that the vesicles from the microsomal membrane fraction actually are unchanged, native vesicles (originating from the ER or Golgi-apparatus) that can fuse with the plasmalemma or the vacuole. Therefore, they can reflect properties of the vacuole or the plasmalemma. The energy dependent acidification within the vesicles, which can be completely reverted through the addition o f CCCP, was determined on the basis o f photometric difference spectra using NR (Hager et al., Z. Naturforsch. 35 c, 7 9 4 -8 0 4 1980). The proton pumps possess a very high substrate specificity; only ATP (+ Mg2+) can be used as substrate, while GTP, ITP, UTP and CTP or other nucleoside tri-or diphosphates cannot be used. DCCD and DES inhibit H +-ATPase completely, oligomycin has only a slight, orthovanadate no inhibitory effect at all. The energy dependent transport o f H+ across the membrane takes place only in the presence of Cl-or Br-(not as well in the presence of I-). Other anions (F~, N O j, SOI-, SC N -, ID A -, H2BOj cannot cause an intravesicular acidification through ATP if chloride (or Br-) is not present. In the presence o f chloride, however, some of these anions inibit the H +/C l--symport (J-, N O j, SO2-, SCN-, H2BO j). They obviously are in competitive interaction with Cl-ions for Cl~-binding sites on a carrier or channel without being able to be transported themselves. Pi, which renders the acidification of the vesicles at a low rate possible without Cl-, is the only tested anion which can augment the Cl-dependent acidification. This supports the idea that either Pi functions as a positive effector on the Cl "-transport or that a Cl ~/Pi-anti porter exists which reduces Cl-accumulation and therefore facilitates the Cl-coupled H + transport into the vesicles also. The anion transport inhibitor, DIDS, blocks the ATP-dependent HMransport. This again supports the idea o f a relatively tight coupling between H + and Cl-transport in a possibly electroneutral system. The presence o f monovalent cations, such as K +, N a+, Li+ and choline*, are not important for H + transport. The dependence o f the ATP-fueled acidification of the vesicles on the same anion pattern which seems to regulate elongation growth and stomata aperture speaks for the eminent importance o f the H +-pump and vesicles described in this report for growth and turgor o f plant cells. 
  Reference    Z. Naturforsch. 36c, 997—1008 (1981); received September 2 1981 
  Published    1981 
  Keywords    Proton Pump, H +-ATPase, Cl--Channel, Coleoptile, Auxin 
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 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-0997.pdf 
 Identifier    ZNC-1981-36c-0997 
 Volume    36 
4Author    A. Hager, P. HermsdorfRequires cookie*
 Title    A H +/Ca2+ Antiporter in Membranes of Microsomal Vesicles from Maize Coleoptiles, a Secondary Energized Ca2+ Pump  
 Abstract    Microsomal vesicles prepared from the ER and the Golgi apparatus o f maize coleoptiles possess an ATP-fueled, Cl_-dependent proton pump which can cause an intravesicular acidifica­ tion of the vesicles (A. Hager. This acidification is very specifically inhibited by Ca2+. The inhibition is already distinct at concentrations o f 30 hm. While 10-fold higher concentrations of La3+ produce similar effects, Mg2+ remains ineffective even at very high concentrations. If Ca2+ is added after acidification o f the vesicles, a rapid H +-efflux proportional to the amount of Ca2+ added characterizes the first reaction phase. In the second reaction phase acidification within the vesicles commences anew, however, at a reduced rate. If Ca2+ is added to vesicles whose proton pump has been inhibited by DCCD, the first reaction phase remains unchanged, while the acidification in the second reaction phase does not set in, and only a leak out o f protons is observed. These results give support for a H +/C a2+-antiporter mechanism which can function as a secondary energized Ca2+-pump and regulate the Ca2+-concentration in the cytoplasm. 
  Reference    Z. Naturforsch. 36c, 1009—1012 (1981); received September 2 1981 
  Published    1981 
  Keywords    Ca2+ Pump, H+-ATPase, Membrane Vesicles, Coleoptile, Zea mays 
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 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-1009.pdf 
 Identifier    ZNC-1981-36c-1009 
 Volume    36 
5Author    Petra Fromme, Ingo Dahse, PeterG. RäberRequires cookie*
 Title    Effect of Tentoxin on the Activation and on the Catalytic Reaction of Reconstituted H +-ATPase from Chloroplasts  
 Abstract    The proton-translocating ATPase from chloroplasts, C F 0Fj, was isolated, purified and re­ constituted into asolectin liposomes. The effect o f the energy transfer inhibitor, tentoxin, on different functions o f the enzyme was investigated. Tentoxin does not inhibit the nucleotide release during energization by a pH /A T jum p, i.e. the activation o f the enzyme is not influ­ enced. ATP synthesis driven by a pH /A T jump and multi-site ATP hydrolysis are completely inhibited by tentoxin, whereas uni-site ATP hydrolysis is not influenced. 
  Reference    Z. Naturforsch. 47c, 239 (1992); received September 30 1991/January 3 1992 
  Published    1992 
  Keywords    H +-ATPase, CF0F, Tentoxin, Enzyme Kinetics, Uni-Site Catalysis 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0239.pdf 
 Identifier    ZNC-1992-47c-0239 
 Volume    47