Figure 1.

(A and B) Snapshot of BtuB in (A) a symmetric bilayer and (B) an asymmetric bilayer. Water is shown as a molecular surface. Ions are shown as yellow for $\text{N}{\text{a}}^{+}$, green for $\text{C}{\text{l}}^{-}$, pink for ${\text{Mg}}^{2+}$, and teal for ${\text{Ca}}^{2+}$. NaCl concentrations are 150 mM in each system. BtuB is represented as orange ribbons. The phospholipid tails are shown in light blue and headgroups are shown as dark blue spheres. Lipid A of LPS is shown in pink, the corresponding lipid A headgroups are shown as magenta spheres, and the core oligosaccharides are shown in red sticks. To see this figure in color, go online.