Figure 5: Ion-binding sites in outward-facing and closed states of BetP.
Structures and ion-binding sites in CeS (colours), Ce (grey) and CcS (tan) states of BetP and BetP-G153D are compared. Sodium ions (violet spheres), and substrate (black sticks) are shown. Changes from the CeS state to the compared state are indicated using arrows. (a–c) Comparisons of substrate-free Ce (PDB entry 4DOJ chain B, grey) and substrate-bound CeS states (colours), showing the effect of substrate binding on the outward-open states on: (a) the overall structure, with helices shown as cylinders; (b) the Na2-binding site, showing protein (ribbons), binding site residues (sticks) and Na2 ion from the CeS structure (sphere). (c) The substrate site (S1) and Na1′ site, with protein shown as ribbons, and with substrate (black) and binding-site residues as sticks. The location of the Na1′ ion is taken from the CeS simulations. (d) Comparison of Na1′ and substrate (S1)-binding site regions in the substrate-bound outward-open (CeS, colours) and the substrate-bound closed (CcS; PDB entry 4AIN chain B, tan) states. The Na1′ ion location is taken from the CeS simulations.
