Figure 2.

Three models of conformational switching. (a) Gating binding site. The binding site switches between being a reflecting boundary to being a radiation boundary. (b) Gated access. A lid along the passageway to the binding site transiently opens and closes, allowing for and blocking the passage of the ligand. (c) Gating binding pocket. The binding site becomes reactive only when the ligand is behind the closed lid. Note that in each model the binding pocket has a cylindrical shape, and a slice along the cylindrical axis is shown. The x axis is along the cylindrical axis.