The FadA filaments were based on the crystal structure of mFadA (Nithianantham et al., 2009), with the addition of intercalating pre-FadA. The signal peptide pairs from two neighboring filaments (one clear bar and one shaded bar) bind to each other through hydrophobic interactions, serving as "hooks" crosslinking the filaments so that the filaments are stacked perpendicular to the fibril axis into fibrous sheets. 