Speaker
Mrs
Anne Bremer
(Max Planck Institute for Molecular Plant Physiology)
Description
The significance of intrinsically disordered proteins (IDPs) has been underestimated for a long time in spite of their high abundance in nature. In fact, it has been predicted that more than 30% of all eukaryotic proteins are IDPs. IDPs have no stable secondary structure in dilute solutions, but instead exist as dynamic ensembles of conformations. We are focusing on the structural and functional characterization of three closely related IDPs from the model plant *Arabidopsis thaliana*. The three IDPs belong to the group of Late Embryogenesis Abundant (LEA) proteins. We expressed the three proteins recombinantly in *E. coli* and found that they are disordered in solution, but mostly α-helical in the dry state, as shown by CD spectroscopy. We showed a linear increase of the α-helical content upon dehydration using a glycerol gradient. Interestingly, the gain of α-helix content was further increased in the presence of artificial membranes. The three LEA proteins protected liposomes from leakage of an encapsulated fluorescent dye during freezing and thawing. Furthermore, X-ray scattering results indicated direct protein-membrane interactions. The interchain distances between the lipids were increased in the presence of the LEA proteins upon dehydration, indicating penetration of the proteins into the membranes. FTIR spectra showed interactions of the proteins with the lipid head groups in the dry state, suggesting a positioning of the proteins in this region parallel to the membrane surface. Recently, we have used neutron membrane diffraction measurements to elucidate the position of the LEA proteins relative to the membranes at different dehydration levels. Detailed data analysis is currently on-going.
Primary author
Mrs
Anne Bremer
(Max Planck Institute for Molecular Plant Physiology)
Co-authors
Dr
Anja Thalhammer
(University Potsdam)
Dr
Benjamin Kent
(Helmholtz-Zentrum Berlin)
Dr
Dirk Hincha
(Max Planck Institute for Molecular Plant Physiology)
Prof.
Gary Bryant
(RMIT University)
