Mercury increases water permeability of a plant aquaporin through a non-cysteine-related mechanism
Journal article, 2013
Water transport across cellular membranes is mediated by a family of membrane proteins known as AQPs (aquaporins). AQPs were first discovered on the basis of their ability to be inhibited by mercurial compounds, an experiment which has followed the AQP field ever since. Although mercury inhibition is most common, many AQPs are mercury insensitive. In plants, regulation of AQPs is important in order to cope with environmental changes. Plant plasma membrane AQPs are known to be gated by phosphorylation, pH and Ca2+. We have previously solved the structure of the spinach AQP SoPIP2;1 (Spinacia oleracea plasma membrane intrinsic protein 2; 1) in closed and open conformations and proposed a mechanism for how this gating can be achieved. To study the effect of mercury on SoPIP2; 1 we solved the structure of the SoPIP2;1-mercury complex and characterized the water transport ability using proteoliposomes. The structure revealed mercury binding to three out of four cysteine residues. In contrast to what is normally seen for AQPs, mercury increased the water transport rate of SoPIP2; 1, an effect which could not be attributed to any of the cysteine residues. This indicates that other factors might influence the effect of mercury on SoPIP2; 1, one of which could be the properties of the lipid bilayer.
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Author
Anna Frick
University of Gothenburg
Michael Järvå
University of Gothenburg
Mikael Ekvall
University of Gothenburg
Povilas Uzdavinys
University of Gothenburg
Anna Maria Nyblom
University of Gothenburg
Susanna Törnroth-Horsefield
University of Gothenburg
Biochemical Journal
0264-6021 (ISSN) 1470-8728 (eISSN)
Vol. 454 pt 3 491-499Subject Categories
Biochemistry and Molecular Biology
DOI
10.1042/bj20130377