/To construct the target binding surface, we stacked the 5-residue fragment of the distinguishable region along the Z-axis, using the screw symmetry of the fibril cryo-EM structure. We then extracted three neighboring strands and used the program MASTER to search for structures in the protein structural databank (PBD) that contained similar backbone coordinates to this motif. This resulted in a large number of helical poses, which were clustered based on the geometry of the interacting helix, its orientation relative to the target binding surface, and its frequency of occurrence (designability).