Figure 3.

The p121-symmetrized projection map of two-dimensional crystals of ABCG2 in the absence of nucleotides and transported substrates. The map was calculated from merged amplitudes and phases from five independent lattices of crystals embedded in vitreous ice. Densities above the mean and negative densities are shown by continuous and dotted lines, respectively. This represents a top view of the two-dimensional crystal along the z axis. The rectangular unit cell (6.98 × 12.25 nm) and the screw axes for plane group p121 have been drawn in. The approximate centre of the noncrystallographic twofold symmetry axis is indicated by an asterisk. The scale bar represents 2.0 nm.