The role of protein hydrophobicity in thionin–phospholipid interactions: a comparison of α1 and α2-purothionin adsorbed anionic phospholipid monolayers
Clifton, L. A., Sanders, M., Kinane, C., Arnold, T., Edler, K. J., Neylon, C., Green, R. J. and Frazier, R. A. (2012) The role of protein hydrophobicity in thionin–phospholipid interactions: a comparison of α1 and α2-purothionin adsorbed anionic phospholipid monolayers. Physical Chemistry Chemical Physics, 14 (39). pp. 13569-13579. ISSN 1463-9076
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To link to this article DOI: 10.1039/C2CP42029E
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 monolayer, 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.
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