Quantification and visualization of protein-membrane and protein-protein interactions

Proteins use specific lipid receptors to attach to the plasma membrane. We are interested in the molecular interaction between membrane-confined receptors and proteins and how this interaction influences the overall membrane structure. In particular, we study the following systems:

Collybistin - phosphatidylinositol phosphate
Receptor recruitment to inhibitory GABAergic and glycinergic synapses is controlled by the scaffold protein gephyrin and the adaptor protein collybistin. Collybistin is a Dbl-family guanine nucleotide exchange factor and is composed of a Dbl-homology (DH) and pleckstrin-homology (PH) domains. In addition, in most collybistin isoforms, an additional N-terminal src-homology 3 (SH3) domain is found. We address the question, which component, i.e. which PIP is responsible for recruiting collybistin to the synaptic membrane by using quantitative methods such as surface plasmon resonance and reflectometric interference spectroscopy.



Ezrin -PIP₂ - F-actin
One of the main players in linking the plasma membrane to the cytoskeleton is the protein ezrin, a member of the ezrin-radixin-moesin (ERM) family. Ezrin is found in a dormant conformation in the cytosol. Once activated, it is localized at the plasma membrane. We investigate, which factors lead to the activation of the protein, which result in the attachment of F-actin. To quantify and visualize ezrin and F-actin binding, we make use of reflectometric interference spectroscopy, fluorescence microscopy and atomic force microscopy. By means of collodial probe microscopy, we were able to determine the binding forces involved in ezrin-F-actin interactions.





Shiga toxin - Gb₃
The bacterial Shiga toxin produced by Shigella dysenteriae and Shiga toxin producing E. coli strains (STECs) gets internalized into the cell after binding of the B-subunits to its natural receptor lipid Gb₃. We analyze, how the molecular structure of the lipid Gb₃ impacts the primary step of internalization of the toxin by a combination of fluorescence and atomic force microscopy.



In part funded by the Deutsche Forschungsgemeinschaft



and
the Max Planck School "Matter to Life"

s. SFB 1286 , RTG 2756 , and Matter to Life