title: The role of protein hydrophobicity in thionin-phospholipid interactions: a comparison of α1 and α2-purothionin adsorbed anionic phospholipid monolayers.
abstract: The plant defence proteins α1- and α2-purothionin (Pth) are type 1 thionins from common wheat (Triticum aestivum). These highly homologous proteins possess characteristics common amongst antimicrobial peptides and proteins, that is, cationic charge, amphiphilicity and hydrophobicity. Both α1- and α2-Pth possess the same net charge, but differ in relative hydrophobicity as determined by C18 reversed phase HPLC. Brewster angle microscopy, X-ray and neutron reflectometry, external reflection FTIR and associated surface pressure measurements demonstrated that α1 and α2-Pth interact strongly with condensed phase 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPG) monolayers at the air/liquid interface. Both thionins disrupted the in-plane structure of the anionic phospholipid monolayers, removing lipid during this process and both penetrated the lipid monolayer in addition to adsorbing as a single protein layer to the lipid head-group. However, analysis of the interfacial structures revealed that the α2-Pth showed faster disruption of the lipid film and removed more phospholipid (12%) from the interface than α1-Pth. Correlating the protein properties and lipid binding activity suggests that hydrophobicity plays a key role in the membrane lipid removal activity of thionins.
authors.affiliation: ISIS Spallation Neutron Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire, UK. Luke.Clifton@stfc.ac.uk
authors.forename: Luke A
authors.initials: LA
authors.lastname: Clifton
authors.forename: Michael
authors.initials: M
authors.lastname: Sanders
authors.forename: Christian
authors.initials: C
authors.lastname: Kinane
authors.forename: Tom
authors.initials: T
authors.lastname: Arnold
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Edler
authors.forename: Cameron
authors.initials: C
authors.lastname: Neylon
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Green
authors.forename: Richard A
authors.initials: RA
authors.lastname: Frazier
mesh_terms: D000327:Adsorption; D000838:Anions / Q000737:chemistry; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D010316:Particle Size; D010743:Phospholipids / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D000838:Anions; D023181:Antimicrobial Cationic Peptides; D010743:Phospholipids; D010940:Plant Proteins; C063948:alpha1-purothionin protein, wheat