Figure 2 - full size

Figure 2. Fig. 2. Structure of the selectivity filter of the wild-type EcClC Fab complex. (A) Stereo view of electron density in the selectivity filter at 2.5 Å, contoured at 1 . The view is from the dimer interface within the membrane. The cytoplasm is on the bottom, the extracellular side on the top. The map was calculated from native amplitudes and solvent-flattened two-fold averaged phases. The refined protein model is shown as sticks. An (F[Br] - F[Cl]) difference Fourier map at 2.8 Å, contoured at 4 , is shown in red. (B) Stereo view of the ion-binding sites. Selected residues in the vicinity of the bound chloride ions are shown. Hydrogen bonds between the protein and chloride ions (red spheres) as well as between the side chain of Glu148 and the rest of the protein are shown as black dashed lines.