| | 2 | Author
| Achim Hager, Roland Frenzel, D. Orothee Laible | Requires 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 | | | |
Similar Items
| Find | | | DEBUG INFO
| | | | | TEI-XML for
| default:Reihe_C/35/ZNC-1980-35c-0783.pdf | | | | Identifier
| ZNC-1980-35c-0783 | | | | Volume
| 35 | |
| 3 | Author
| A. Hager, M. H. Elm Le | Requires 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 | | | |
Similar Items
| Find | | | DEBUG INFO
| | | | | TEI-XML for
| default:Reihe_C/36/ZNC-1981-36c-0997.pdf | | | | Identifier
| ZNC-1981-36c-0997 | | | | Volume
| 36 | |
| 4 | Author
| A. Hager | Requires cookie* | | | Title
| A vena Coleoptile Segments: Hyperelongation Growth after Anaerobic Treatment | | | | Abstract
| Avena sativa coleoptile segments show an anomalous increase in elongation growth following a short period of oxygen deprivation (tested between 0 and 60 min) lasting 20-30 min (^«aero-biosis-^erobiosis transition effect = ANA effect). The increase in growth rate is 600% and is commensurate with that observable following an auxin treatment. This hyperelongation growth, in contrast to the auxin-induced growth, begins without a lag phase. The growth "burst" following anaerobiosis is similarly to auxin-induced elongation growth, and is suppressed increasingly by neutral or more alkaline buffers. Hyperelongation growth is suppressed by respiratory inhibitors and uncouplers. A complete inhibition is effected with KCN (0.5 mM) sodium azide (0.5 mM) and CCCP (1 |iM); amytal (in the range 0.5 to 1 mM) and sodium arsenate (0.1 to 1 mM) are strong inhibitors. Some of these compounds (KCN, arsenate, amytal) cause a slight increase of the ANA effect in very low concentrations, which is probably due to the K+ or Na+ ions present; on their own, these ions have a strong positive influence on the ANA effect. During anaerobiosis the ATP level sinks around 75% and almost returns to the old value, following the supply of air, within one minute. The cell sap pH drops from 6.3 to 5.9 during anaerobiosis within 20 min. This lowering is mainly due to an increase in lactic acid concentration. Other acids such as citric, malic, and aspartic acids show insignificant changes in concentration. The NADH content increases during anaerobiosis, whereas that of NADPH drops almost as much. The mentioned changes in concentration of lactic acid, NADH and NADPH return to the control value within 20-30 min; thus the differences exist as long as hyperelongation growth is under way. Possible relationships between the mentioned chemical changes and hyperelongation growth are discussed. One of the possible explanations is the following: the lowering of the cytoplasmic pH (normally around pH 7) during anaerobiosis due to the formation of lactic acid causes an activation of H+-ATPases in the plasmalemma and ER, since their optimum activity occurs in a pH of 5.5 to 6.5. This activation causes a greater H+-excretion into the cell wall compartment, and thus hyperelongation growth following supply of air and of ATP. | | | |
Reference
| Z. Naturforsch. 35c, 794—804 (1980); received July 12 1980 | | | |
Published
| 1980 | | | |
Keywords
| Avena Coleoptile, Elongation Growth, Anoxia, Auxin, NAD(P)H, Proton Pump | | | |
Similar Items
| Find | | | DEBUG INFO
| | | | | TEI-XML for
| default:Reihe_C/35/ZNC-1980-35c-0794.pdf | | | | Identifier
| ZNC-1980-35c-0794 | | | | Volume
| 35 | |
|
