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Increased Permeability of the Aquaporin SoPIP2;1 by Mercury and Mutations in Loop A

Kirscht, Andreas LU ; Survery, Sabeen LU ; Kjellbom, Per LU and Johanson, Urban LU (2016) In Frontiers in Plant Science 7. p.1-11
Abstract

Aquaporins (AQPs) also referred to as Major intrinsic proteins, regulate permeability of biological membranes for water and other uncharged small polar molecules. Plants encode more AQPs than other organisms and just one of the four AQP subfamilies in Arabidopsis thaliana, the water specific plasma membrane intrinsic proteins (PIPs), has 13 isoforms, the same number as the total AQPs encoded by the entire human genome. The PIPs are more conserved than other plant AQPs and here we demonstrate that a cysteine residue, in loop A of SoPIP2;1 from Spinacia oleracea, is forming disulfide bridges. This is in agreement with studies on maize PIPs, but in contrast we also show an increased permeability of mutants with a substitution at this... (More)

Aquaporins (AQPs) also referred to as Major intrinsic proteins, regulate permeability of biological membranes for water and other uncharged small polar molecules. Plants encode more AQPs than other organisms and just one of the four AQP subfamilies in Arabidopsis thaliana, the water specific plasma membrane intrinsic proteins (PIPs), has 13 isoforms, the same number as the total AQPs encoded by the entire human genome. The PIPs are more conserved than other plant AQPs and here we demonstrate that a cysteine residue, in loop A of SoPIP2;1 from Spinacia oleracea, is forming disulfide bridges. This is in agreement with studies on maize PIPs, but in contrast we also show an increased permeability of mutants with a substitution at this position. In accordance with earlier findings, we confirm that mercury increases water permeability of both wild type and mutant proteins. We report on the slow kinetics and reversibility of the activation, and on quenching of intrinsic tryptophan fluorescence as a potential reporter of conformational changes associated with activation. Hence, previous studies in plants based on the assumption of mercury as a general AQP blocker have to be reevaluated, whereas mercury and fluorescence studies of isolated PIPs provide new means to follow structural changes dynamically.

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publication status
published
subject
keywords
Journal Article
in
Frontiers in Plant Science
volume
7
pages
11 pages
publisher
Frontiers
external identifiers
  • Scopus:84986559278
ISSN
1664-462X
DOI
10.3389/fpls.2016.01249
language
English
LU publication?
yes
id
468f5ba5-23ea-460f-9f00-acb4c3bee882
date added to LUP
2016-10-11 10:15:00
date last changed
2016-11-03 14:08:45
@misc{468f5ba5-23ea-460f-9f00-acb4c3bee882,
  abstract     = {<p>Aquaporins (AQPs) also referred to as Major intrinsic proteins, regulate permeability of biological membranes for water and other uncharged small polar molecules. Plants encode more AQPs than other organisms and just one of the four AQP subfamilies in Arabidopsis thaliana, the water specific plasma membrane intrinsic proteins (PIPs), has 13 isoforms, the same number as the total AQPs encoded by the entire human genome. The PIPs are more conserved than other plant AQPs and here we demonstrate that a cysteine residue, in loop A of SoPIP2;1 from Spinacia oleracea, is forming disulfide bridges. This is in agreement with studies on maize PIPs, but in contrast we also show an increased permeability of mutants with a substitution at this position. In accordance with earlier findings, we confirm that mercury increases water permeability of both wild type and mutant proteins. We report on the slow kinetics and reversibility of the activation, and on quenching of intrinsic tryptophan fluorescence as a potential reporter of conformational changes associated with activation. Hence, previous studies in plants based on the assumption of mercury as a general AQP blocker have to be reevaluated, whereas mercury and fluorescence studies of isolated PIPs provide new means to follow structural changes dynamically.</p>},
  author       = {Kirscht, Andreas and Survery, Sabeen and Kjellbom, Per and Johanson, Urban},
  issn         = {1664-462X},
  keyword      = {Journal Article},
  language     = {eng},
  month        = {08},
  pages        = {1--11},
  publisher    = {ARRAY(0xb6ae0e8)},
  series       = {Frontiers in Plant Science},
  title        = {Increased Permeability of the Aquaporin SoPIP2;1 by Mercury and Mutations in Loop A},
  url          = {http://dx.doi.org/10.3389/fpls.2016.01249},
  volume       = {7},
  year         = {2016},
}