The unusual behaviour of a plant seed defence protein

Structures of Puroindoline

Structures of puroindoline-a micelle (top) and monomer (bottom) obtained from small angle neutron scattering, dynamic light scattering, and size-exclusion chromatography.
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Using a combination of techniques, the unique structure of an important plant defense protein is discovered, which could have implications in drug delivery systems and antibiotics.

A combination of small angle neutron scattering, dynamic light scattering and size-exclusion chromatography has been used to uncover a protein's unique structuring behaviour in solution.

Puroindoline-a is a plant seed defence protein found in wheat. It has a broad spectrum of antifungal and antibacterial activity, and has potential applications such as novel antibiotics or targeted drug delivery systems.

Puroindoline-a forms micelles in aqueous solution. One part of a puroindoline-a molecule is water-loving; the other end is water-insoluble. Micelles are groups of the protein molecules in which the water-loving parts all point outwards, into the surrounding solution. Proteins which form micelles are rare, with only one other protein known to spontaneously form these assemblies in solution. We have been able to discover that the structure formed by puroindoline-a is unique amongst known protein micelles, being highly elongated rather than spherical. Puroindolines contain a tryptophan-rich part which is responsible for the protein’s antimicrobial membrane-binding activity. This part is also thought to be responsible for its solution-structuring behaviour, with this region forming the water-insoluble interior of the micelle.

LA Clifton, MR Sanders, SE Rogers, RK Heenan, C Neylon (ISIS), V Castelletto, RA Frazier, RJ Green (University of Reading)

Research date: August 2011

Further Information

Contact: Dr LA Clifton, luke.clifton@stfc.ac.uk; Dr RA Frazier, r.a.frazier@reading.ac.uk


Further reading: LA Clifton et al., Phys. Chem. Chem. Phys. 13 (2011) 8881

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