Figure 4.

F233 is stabilized by van der Waals interactions to its neighbors. (A) Interaction energies between F233 and neighbor residues, with important residues marked in bold. Several neighbors appear to stabilize the blocked orientation of the lock. I230 shows the strongest interactions with energies approaching 15 kJ/mol. The F233 ring starts to rotate after 1 Å of translation, which is also where the interactions are reduced. After R4 has crossed (4–5 Å) the ring rotates back and regains its interactions. (B) Corresponding phenyl ring rotation around χ² as a function of S4 translation. The hydrophobic residues in a semicircle above (C) and around (D) F233 help shield/stabilize the side chain (E) and favor the extracellular rotation of the phenyl ring.