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Membrane binding of disordered plant dehydrins is tuned by phosphorylation and coordination of Ca2+ and Zn2+ ions.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.ORCID iD: 0000-0003-2749-2415
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Dehydrins are intrinsically disordered proteins expressed under water- related stress in plants. As a clue to their function, some dehydrins are found to interact in an orderly manner with negatively-charged lipids, supporting the idea of a key role in safeguarding membrane integrity. We have earlier reported that this lipid interaction is modulated electrostatically. Of particular interest is the pronounced effect of local charge that shed light on how dehydrin function is regulated in vivo. In this study we test the generality of this proposition on four dehydrins from Arabidopsis thaliana representing different dehydrin subgroups. The results show that membrane interaction of dehydrins in their apo state is correlated to their protein net charge. Also, we explore further putative regulation mechanism by investigating the additive role of ion coordination and phosphorylation on membrane binding. The results show that coordination of Ca2+ and Zn2+ have markedly different effects. Coordination of Ca2+ augments mainly the membrane affinity of dehydrins that already bind lipids in their apo states (Lti30 and Rab18). Coordination of Zn2+, on the other hand, induces membrane binding and vesicle assembly of all tested proteins, also those that fail to bind membranes in the absence of metal ions (Cor47 or Lti29). Finally, we observe that the effect of Ca2+ is effectively enhanced by phosphorylation. The observations corroborate the idea of a sensitive and multifaceted regulatory mechanism of the dehydrin function in stressed plant cells but point also at a functional diversity. 

Keyword [en]
Dehydrin, intrinsically disordered proteins, Lea-proteins, membrane binding, calcium, zinc, phosphorylation
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:su:diva-136023OAI: oai:DiVA.org:su-136023DiVA: diva2:1050496
Available from: 2016-11-29 Created: 2016-11-29 Last updated: 2017-01-10Bibliographically 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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