Gating mechanisms for biological electron transfer: Integrating structure with biophysics reveals the nature of redox control in cytochrome P450 reductase and copper-dependent nitrite reductase

► Electron transfer in cytochrome P450 reductase is conformationally gated. ► Chemical gating of electron transfer occurs in copper-dependent nitrite reductase. ► Elucidation of gating mechanisms requires integrated programmes dependent on structural and biophysical approaches.