Fig. 2: Cryo-EM analysis of the AlbAB filament.

a, Representative 2D class averages of filament particles, demonstrating two distinct subunits corresponding to AlbA₂ and AlbB₂ arranged in a periodic assembly. b, Cryo-EM density resulting from a helical reconstruction of the AlbAB filament. AlbA₂ and AlbB₂ dimers are shown in dark blue and light blue, respectively. c, Surface representation of the refined models for AlbA₂ and AlbB₂ assembled into a filament highlighting the geometric parameters of the helical filament. d, View facing down the long axis of the filament highlighting its right-handedness. e, Ribbon representation of the biologically relevant asymmetric unit of the AlbAB filament containing a dimer of AlbA and a dimer of AlbB in a heterotetrametric assembly. Covalently bound FMN cofactors are shown (yellow, spheres), highlighting their proximity to the AlbA₂-AlbB₂ interface. f, Ribbon representation of a dimer of AlbA₂ with FMN shown (yellow, spheres). g, Ribbon representation of the AlbB₂ dimer.