Tonoplast localization of a calmodulin-stimulated Ca2+-pump from maize roots.

Détails

ID Serval
serval:BIB_3875
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Institution
Titre
Tonoplast localization of a calmodulin-stimulated Ca2+-pump from maize roots.
Périodique
Plant Science
Auteur⸱e⸱s
Gavin O., Pilet P.E., Chanson A.
ISSN
0168-9452
Statut éditorial
Publié
Date de publication
1993
Volume
92
Numéro
2
Pages
143-150
Langue
anglais
Résumé
The subcellular localization of a calmodulin-stimulated calcium (Ca2+)-ATPase activity from maize roots (Zea mays L., cv LG 11) was studied. For this purpose, an efficient procedure was developed to prepare sealed plasma membrane vesicles allowing the measurement of proton and Ca2+ transport activities. Two-day-old root membranes were fractionated by sucrose and dextran density gradient centrifugation. Marker enzymes were used to study the distribution of the different membranes in the gradients and a filtration technique was developed to measure Ca-45(2+) transport in sealed vesicles. Most of the ATP-dependent Ca2+ transport activity was associated with the ER. However, a small part of this activity was associated with the tonoplast (corresponding to the activity of the H+/Ca2+ antiport) and the plasma membrane. When the Ca2+ transport was measured in the presence of exogenous calmodulin (1 muM), a 3-5-fold increase of uptake was measured. The calmodulin-stimulated activity was associated with the tonoplast vesicles only. This activity was insensitive to monensin, a proton ionophore, ruling out a direct effect of calmodulin on the H+/Ca2+ antiport. In conclusion, four different Ca2+ transporters are present in young maize root cells. A Ca2+/H+ antiport system is present on the tonoplast, whereas, the plasma membrane and the ER possess each a calmodulinin-sensitive Ca2+-ATPase. Finally, a calmodulin-stimulated Ca2+-ATPase is associated with the tonoplast.
Mots-clé
CA2+-ATPASE, CALMODULIN, MARKER ENZYMES, TONOPLAST, ENDOPLASMIC RETICULUM, ROOT, ZEA-MAYS L
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Création de la notice
19/11/2007 10:14
Dernière modification de la notice
20/08/2019 13:27
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