Steps in structure determination of tubular crystals grown from EDTA-treated YiiP. (A) Representative micrograph. (B) Selection of 2-D class averages showing different helical symmetries: purple outline for tubes with D1 symmetry, green outline for tubes with D3 symmetry, and yellow outline for other, uncharacterized symmetries. (C) Helical reconstructions of tubular crystals with D1 and D3 symmetry. One dimer from the helical array has been colored. (D) Masked dimers from each of the reconstructions colored according to the local resolution ranging from 4.1 to 6.5 Å. The Fourier shell correlation (FSC) plot for each reconstruction is also shown, indicating an overall resolution of 4.2 Å.