Exploring membrane activity of plant seed defence proteins

interaction of puroindoline-a with an anionic phospholipid monolayer

Neutron reflectivity data and associated scattering length density profile for the interaction of puroindoline-a with an anionic phospholipid monolayer. The schematic shows the interfacial layer structure.

Plants are constantly exposed to pathogens and, in response, have developed multiple defence mechanisms that include the expression of antimicrobial proteins.

These are characterised by having high structural and thermodynamic stability, but their precise mechanism of action is not known. However, it is widely accepted that these proteins act at the level of the cell membrane.

We have investigated the membrane interactions of the puroindolines, a family of antimicrobial proteins found in wheat. The puroindolines are unique among plant proteins as they contain a tryptophan-rich domain and play an additional role in determining wheat endosperm texture, an economically important quality that determines the milling characteristics of wheat.

The tryptophan-rich domain is thought to be implicated in the membrane interactions of puroindolines. Using air/liquid monolayer and solid/liquid floating bilayer models, we have used neutron reflectivity to explore how single amino-acid residue substitutions affect a protein’s ability to penetrate lipid membranes, as well as how these findings relate to antimicrobial effectiveness.

LA Clifton (ISIS), RA Frazier, RJ Green (Reading University), AV Hughes (ISIS)

Research date: January 2010

Further Information

Contact: Dr LA Clifton, luke.clifton@stfc.ac.uk; Dr RJ Green, rebecca.green@reading.ac.uk

Further reading: LA Clifton et al., J Phys Chem B 112 (2008) 15907

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