TU Darmstadt / ULB / TUbiblio

On the pH regulation of plant aquaporins.

Fischer, Matthias and Kaldenhoff, Ralf (2008):
On the pH regulation of plant aquaporins.
In: The Journal of biological chemistry, pp. 33889-92, 283, (49), ISSN 0021-9258,
[Article]

Abstract

The majority of plants are unable to evade unfavorable conditions such as flooding, salinity, or drought. Therefore, a fine-tuned water homeostasis appears to be of crucial importance for plant survival, and it was assumed that aquaporins play a significant role in these processes. Regulation of plant aquaporin conductivity was suggested to be achieved by a gating mechanism that involves protein phosphorylation under drought stress conditions and protonation after cytosolic acidification during flooding. The effect of protein phosphorylation or protonation of aquaporins was studied on two plasma membrane intrinsic proteins, NtPIP2;1 and NtAQP1 from tobacco, which were heterologously expressed in yeast. Our results on mutated aquaporins with serine-to-alanine exchange indicate that phosphorylation of the two key serine residues did not affect the pH-dependent modification of water permeability. Protonation on a conserved histidine residue decreased water conductivity of NtPIP2;1. Although cells expressing NtPIP2;1 with a replacement of the histidine by an alanine were found to be pH-insensitive with regard to water permeability, these maintain high water transport rates, similar to those obtained under acidic conditions. The data clearly support the role of histidine at 196 as a component of pH-dependent modification of aquaporin-facilitated water transport. The predictions of combined effects from phosphorylation at conserved serines and histidine protonation were not supported by the results of functional analysis. The obtained results challenge the gating model as a general regulation mechanism for plant plasma membrane aquaporins.

Item Type: Article
Erschienen: 2008
Creators: Fischer, Matthias and Kaldenhoff, Ralf
Title: On the pH regulation of plant aquaporins.
Language: English
Abstract:

The majority of plants are unable to evade unfavorable conditions such as flooding, salinity, or drought. Therefore, a fine-tuned water homeostasis appears to be of crucial importance for plant survival, and it was assumed that aquaporins play a significant role in these processes. Regulation of plant aquaporin conductivity was suggested to be achieved by a gating mechanism that involves protein phosphorylation under drought stress conditions and protonation after cytosolic acidification during flooding. The effect of protein phosphorylation or protonation of aquaporins was studied on two plasma membrane intrinsic proteins, NtPIP2;1 and NtAQP1 from tobacco, which were heterologously expressed in yeast. Our results on mutated aquaporins with serine-to-alanine exchange indicate that phosphorylation of the two key serine residues did not affect the pH-dependent modification of water permeability. Protonation on a conserved histidine residue decreased water conductivity of NtPIP2;1. Although cells expressing NtPIP2;1 with a replacement of the histidine by an alanine were found to be pH-insensitive with regard to water permeability, these maintain high water transport rates, similar to those obtained under acidic conditions. The data clearly support the role of histidine at 196 as a component of pH-dependent modification of aquaporin-facilitated water transport. The predictions of combined effects from phosphorylation at conserved serines and histidine protonation were not supported by the results of functional analysis. The obtained results challenge the gating model as a general regulation mechanism for plant plasma membrane aquaporins.

Journal or Publication Title: The Journal of biological chemistry
Volume: 283
Number: 49
Divisions: 10 Department of Biology > Applied Plant Sciences
?? fb10_botanik ??
10 Department of Biology
Date Deposited: 31 Aug 2011 12:03
Export:
Suche nach Titel in: TUfind oder in Google

Optionen (nur für Redakteure)

View Item View Item