CW and Pulse EPR of Cytochrome P450 to Determine Structure and Function

Cytochromes P450 (P450s) are a diverse class of biological monooxygenases found in a wide variety of organisms, known for their chemical versatility and reaction specificity. While an array of chemical techniques are available to study P450s, continuous wave (CW) and pulse electron paramagnetic resonance (EPR) spectroscopies provide unique insight into the structure and function of the protein by probing various paramagnetic states. In this review we will demonstrate how EPR techniques are used to reveal information about the arrangement and conformation of P450 electron-transport protein complexes, characterise the active site oxidation state and the interactions with substrates and inhibitors. In addition, when combined with sample preparation using cryoreduction and freeze-quench techniques, EPR can be used to characterise short-lived intermediates formed during the catalytic cycle.