Speaker
Dr
Luke Clifton
(ISIS Spallation Neutron and Muon Source)
Description
Indolines and thionins are cationic, amphiphillic, antimicrobial proteins found in a series of cereal species. The antimicrobial activity of both protein families is thought to be related to their ability to disrupt pathogen membrane function via direct interactions with the lipid component of the membrane. We have been examining the lipid binding activity of a series of indoline and thionin types and comparing the molecular solution structuring to the nature of the hydrophobic surface of the proteins.
The hydrophobic region of the puroindolines is a unique Tryptophan rich domain which is fully conserved on the major isoform puroindoline-a and partially conserved on the minor isoform puroindoline-b. We have shown that puroindoline-a uniquely forms highly prolate protein micelles in solution. This self assembly is likely driven by the amphiphillic nature of the molecule and in particular the hydrophobicity of the Trp rich domain. During its lipid binding interactions with phospholipid monolayers the protein is unable to penetrate the lipid acyl chain region on condense phase anionic phospholipid monolayers probably due to the interactions between the tryptophans and the lipid carbonyl groups.
Conversely, all thionin types examined showed high penetration into condense phase DPPG monolayers, as well as removing lipids from the interface during the protein adsorption process. When comparing the lipid binding interactions of α1 and α2-purothionin, two highly related protein which are similar in charge but differ in their relative hydrophobicity (with α2-Pth being more hydrophobic than α1-Pth), we observed a correlation between the ability of these protein to remove lipids from the interface, with the more hydrophobic protein able to remove more lipid from the interface.
These findings have implication for our understanding of the role of small cationic amphiphillic proteins in defending the seed endosperm from bacterial and fungal pathogens and in the indolines role in wheat endosperm hardness.
| Topic Area / Session | Lipids |
|---|
Primary author
Dr
Luke Clifton
(ISIS Spallation Neutron and Muon Source)
Co-authors
Dr
Rebecca Green
(Reading university)
Prof.
Richard Frazier
(Reading university)
