Structural and functional characterization of the Curli adaptor protein CsgF

Curli are functional amyloids that form a major part of the biofilm produced by many enterobacteriaceae. A multiprotein system around the outer membrane protein CsgG is in charge of the export and controlled propagation of the main Curli subunits, CsgA and CsgB. CsgF is essential for the linkage of the main amyloid-forming proteins to the cell surface. Here, we present a profound biochemical and biophysical characterization of recombinant CsgF, highlighted by a solution NMR structure of CsgF in the presence of dihexanoylphosphocholine micelles. Interestingly, CsgF contains large unstructured domains and does not show a globular fold. The data presented shed new light on the molecular mechanism of Curli amyloid surface attachment.