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Mimicking the Plant Cell Interior under Water Stress by Macromolecular Crowding: Disordered Dehydrin Proteins Are Highly Resistant to Structural Collapse
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
2008 (English)In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 148, no 4, 1925-1937 p.Article in journal (Refereed) Published
Abstract [en]

The dehydrins are a class of drought-induced proteins in plants that lack a fixed three-dimensional structure. Their specific molecular action, as well as the reason for their disordered character, is as yet poorly understood. It has been speculated, however, that the dehydrins are tuned to acquire a biologically active structure only under the conditions at which they normally function, i.e. upon dehydration. To test this idea, we here investigate the effect of reduced water content and macromolecular crowding on three dehydrins from Arabidopsis thaliana. As a simplistic model for mimicking cellular dehydration we used polyethylene glycol (PEG), glycerol, and sugars which plants naturally employ as compatible solutes, i.e. sucrose and glucose. Macromolecular crowding was induced by the large polysaccharides ficoll and dextran. The results show that the dehydrins are remarkably stable in their disordered state and are only modestly affected by the solvent alterations. A notable exception is the dehydrin Cor47 which shows a small, intrinsic increase in helical structure at high concentrations of osmolytes. We also examined the effect of phosphorylation but found no evidence that such post-translational modifications of the dehydrin sequences modulate their structural response to osmolytes and crowding agents. The results suggest that the dehydrins are highly specialised proteins that have evolved to maintain their disordered character under conditions where unfolded states of several globular proteins would tend to collapse.

Place, publisher, year, edition, pages
2008. Vol. 148, no 4, 1925-1937 p.
Keyword [en]
dehydrin, intrinsically disordered protein, macromolecular crowding, circular dichroism (CD)
National Category
Biological Sciences
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:su:diva-17653DOI: 10.1104/pp.108.124099ISI: 000261501500016OAI: oai:DiVA.org:su-17653DiVA: diva2:184174
Available from: 2009-01-19 Created: 2009-01-19 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Molecular properties of disordered plant dehydrins: Membrane interaction and function in stress
Open this publication in new window or tab >>Molecular properties of disordered plant dehydrins: Membrane interaction and function in stress
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Dehydrins are intrinsically disordered plant stress-proteins. Repetitively in their sequence are some highly conserved stretches of 7-17 residues, the so called K-, S-, Y- and lysine rich segments. This thesis aims to give insight into the possible role dehydrins have in the stressed plant cell with main focus on membrane interaction and protection. The work includes four recombinant dehydrins from the plant Arabidopsis thaliana: Cor47 (SK3), Lti29 (SK3), Lti30 (K6) and Rab18 (Y2SK2).

Initially, we mimicked crowded cellular environment in vitro to verify that dehydrins are truly disordered proteins. Thereafter, the proposal that the compulsory K-segment determines membrane binding was tested. Experiments show that only Lti30 and Rab18 bind, whereas Cor47 and Lti29 does not. As Lti30 and Rab18 binds they assembles vesicles into clusters in vitro, a feature used to characterize the interaction. From this it was shown that membrane binding of Lti30 is electrostatic and determined by global as well as local charges. Protonation of histidine pairs flanking the K-segments works as an on/off-binding switch. By NMR studies it was shown that the K-segments form a dynamic α-helix upon binding, so called disorder-to-order behaviour. Also, dehydrins electrostatic interaction with lipids can be further tuned by posttranslational phosphorylation or coordination of calcium and zinc ions.

Finally, specific binding of Rab18 to inositol lipids, mainly PI(4,5)P2, is reported. The interaction is mainly coordinated by two arginines neighboring one of the K-segments. In conclusion, the K-segments are indeed involved in the binding of dehydrins to membrane but only in combination with extensions (Lti30) or modified (Rab18). 

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2016. 62 p.
Keyword
abiotic stress, dehydrin, intrinsically disordered proteins, Lea-proteins, phospholipids
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
urn:nbn:se:su:diva-136033 (URN)978-91-7649-065-5 (ISBN)978-91-7649-599-5 (ISBN)
Public defence
2017-01-13, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.

Available from: 2016-12-20 Created: 2016-11-29 Last updated: 2016-12-21Bibliographically approved

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