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The plant defensin NaD1 introduces membrane disorder through a specific interaction with the lipid, phosphatidylinositol 4,5 bisphosphate

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© 2016 Elsevier B.V. All rights reserved. Plant defensins interact with phospholipids in bilayers as part of their cytotoxic activity. Solanaceous class II defensins with the loop 5 sequence pattern "S-[KR]-[ILVQ]-[ILVQ]-[KR]-[KR]" interact with PI(4,5)P2. Here, the prototypical defensin of this class, NaD1, is used to characterise the biophysical interactions between these defensins and phospholipid bilayers. Binding of NaD1 to bilayers containing PI(4,5)P2 occurs rapidly and the interaction is very strong. Dual polarisation interferometry revealed that NaD1 does not dissociate from bilayers containing PI(4,5)P2. Binding of NaD1 to bilayers with or without PI(4,5)P2 induced disorder in the bilayer. However, permeabilisation assays revealed that NaD1 only permeabilised liposomes with PI(4,5)P2 in the bilayer, suggesting a role for this protein-lipid interaction in the plasma membrane permeabilising activity of this defensin. No defensins in the available databases have the PI(4,5)P2 binding sequence outside the solanaceous class II defensins, leading to the hypothesis that PI(4,5)P2 binding co-evolved with the C-terminal propeptide to protect the host cell against the effects of the tight binding of these defensins to their cognate lipid as they travel along the secretory pathway. This data has allowed us to develop a new model to explain how this class of defensins permeabilises plasma membranes to kill target cells.

Funding

MAA and NLV are funded by the Australian Research Council (DP150104386).MIA acknowledges the support of the National Health and Medical Research Council (#1044327) and the Australian Research Council (DP1110101866).

History

Publication Date

01/01/2016

Journal

Biochimica et Biophysica Acta (BBA) - Biomembranes

Volume

1858

Issue

6

Pagination

11p. (p. 1099-1109)

Publisher

Elsevier

ISSN

0005-2736

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