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The role of protein hydrophobicity in thionin–phospholipid interactions: a comparison of alpha 1 and alpha 2-purothionin adsorbed anionic phospholipid monolayers

DOI: 10.1039/c2cp42029e DOI Help

Authors: Luke Clifton (ISIS) , Michael Sanders (University of Reading, U.K.) , Christy Kinane (ISIS Pulsed Neutron and Muon Source) , Tom Arnold (Diamond Light Source) , Karen J. Edler (University of Reading) , Cameron Neylon (ISIS Spallation Neutron Source, Science and Technology Facilities Council) , Rebecca Green (University of Reading) , Richard Frazier (University of Reading)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Chemistry Chemical Physics , VOL 14 (39) , PAGES 13569-13579

State: Published (Approved)
Published: August 2012
Diamond Proposal Number(s): 6306

Abstract: The plant defence proteins ?1- and ?2-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 ?1- and ?2-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 ?1 and ?2-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 ?2-Pth showed faster disruption of the lipid film and removed more phospholipid (12%) from the interface than ?1-Pth. Correlating the protein properties and lipid binding activity suggests that hydrophobicity plays a key role in the membrane lipid removal activity of thionins.

Journal Keywords: Plant Defence Proteins; Triticum Aestivum; Cationic Charge; Amphiphilicity; Hydrophobicity;

Subject Areas: Biology and Bio-materials

Instruments: I07-Surface & interface diffraction