title: The plant defensin NaD1 introduces membrane disorder through a specific interaction with the lipid, phosphatidylinositol 4,5 bisphosphate.
abstract: 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.
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
authors.forename: Jennifer A E
authors.initials: JA
authors.lastname: Payne
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Bleackley
authors.affiliation: Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Tzong-Hsien
authors.initials: TH
authors.lastname: Lee
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
authors.forename: Thomas M A
authors.initials: TM
authors.lastname: Shafee
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
authors.forename: Ivan K H
authors.initials: IK
authors.lastname: Poon
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Hulett
authors.affiliation: Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Marie-Isabel
authors.initials: MI
authors.lastname: Aguilar
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
authors.forename: Nicole L
authors.initials: NL
authors.lastname: van der Weerden
authors.affiliation: Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia. Electronic address: m.anderson@latrobe.edu.au.
authors.forename: Marilyn A
authors.initials: MA
authors.lastname: Anderson
mesh_terms: D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000502:physiology*; D008051:Lipid Bilayers; D008563:Membrane Lipids / Q000378:metabolism*; D008969:Molecular Sequence Data; D009245:NADH Dehydrogenase / Q000737:chemistry / Q000502:physiology*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; D008051:Lipid Bilayers; D008563:Membrane Lipids; D019269:Phosphatidylinositol 4,5-Diphosphate; D009245:NADH Dehydrogenase; C000594053:Nad1 protein, Arabidopsis
keywords: Kinetics; Membrane disorder; Membrane fusion; Phosphatidylinositol 4,5 bisphosphate; Plant defensin; Protein–lipid interaction