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Titolo:
ON THE MECHANISM OF HYPERACIDIFICATION IN LEMON - COMPARISON OF THE VACUOLAR H-ATPASE ACTIVITIES OF FRUITS AND EPICOTYLS()
Autore:
MULLER ML; IRKENSKIESECKER U; RUBINSTEIN B; TAIZ L;
Indirizzi:
UNIV CALIF SANTA CRUZ,DEPT BIOL,SINSHEIMER LABS SANTA CRUZ CA 95064 UNIV CALIF SANTA CRUZ,DEPT BIOL,SINSHEIMER LABS SANTA CRUZ CA 95064 UNIV MASSACHUSETTS,DEPT BIOL AMHERST MA 01003
Titolo Testata:
The Journal of biological chemistry
fascicolo: 4, volume: 271, anno: 1996,
pagine: 1916 - 1924
SICI:
0021-9258(1996)271:4<1916:OTMOHI>2.0.ZU;2-V
Fonte:
ISI
Lingua:
ENG
Soggetto:
DEPENDENT PROTON PUMP; BETA-VULGARIS; MAMMALIAN KIDNEY; CORN COLEOPTILES; STORAGE TISSUE; ACIDIFICATION; INHIBITOR; MEMBRANE; ACID; PURIFICATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
38
Recensione:
Indirizzi per estratti:
Citazione:
M.L. Muller et al., "ON THE MECHANISM OF HYPERACIDIFICATION IN LEMON - COMPARISON OF THE VACUOLAR H-ATPASE ACTIVITIES OF FRUITS AND EPICOTYLS()", The Journal of biological chemistry, 271(4), 1996, pp. 1916-1924

Abstract

Lemon fruit vacuoles acidify their lumens to pH 2.5, 3 pH units lowerthan typical plant vacuoles. To study the mechanism of hyperacidification, the kinetics of ATP-driven proton pumping by tonoplast vesicles from lemon fruits and epicotyls were compared. Fruit vacuolar membranes were less permeable to protons than epicotyl membranes. H+ pumping by epicotyl membranes was chloride-dependent, stimulated by sulfate, and inhibited by the classical vacuolar ATPase (V-ATPase) inhibitors nitrate, bafilomycin, N-ethylmaleimide, and N,N'-dicyclohexylcarbodiimide. In addition, the epicotyl H+ pumping activity was inactivated by oxidation at room temperature, and oxidation was reversed by dithiothreitol. Cold inactivation of the epicotyl V-ATPase by nitrate (greater than or equal to 100 mM) was correlated with the release of V-1 complexesfrom the membrane. In contrast, H+ pumping by the fruit tonoplast-enriched membranes was chloride-independent, largely insensitive to the V-ATPase inhibitors, and resistant to oxidation. Unlike the epicotyl H+-ATPase, the fruit H+-ATPase activity was partially inhibited by 200 mu M vanadate. Cold inactivation treatment failed to inhibit H+ pumpingactivity of the fruit membranes, even though immunoblots showed that V-1 complexes were released from the membrane. However, cold inactivation doubled the percent inhibition by 200 mu M vanadate from 30% to 60%. These results suggest the presence of two H+-ATPases in the fruit preparation: a V-ATPase and an unidentified vanadate-sensitive H+-ATPase. Attempts to separate the two activities in their native membranes on linear sucrose density gradients were unsuccessful. However, following detergent-solubilization and centrifugation on a glycerol density gradient, the two ATPase activities were resolved: a nitrate-sensitive V-type ATPase that is also partially inhibited by 200 mu M vanadate, and an apparently novel vanadate-sensitive ATPase that is also partially inhibited by nitrate.

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Documento generato il 27/11/20 alle ore 10:33:50