Effect of redox partner binding on CYP101D1 conformational dynamics

Area of Science:

• Biochemistry
• Structural Biology
• Enzyme kinetics

Background:

• Cytochrome P450 enzymes (P450s) are crucial for metabolism and drug detoxification.
• P450cam and its homologue CYP101D1 share structural similarities but exhibit functional differences.
• Understanding substrate and redox partner interactions is key to P450 function.

Purpose of the Study:

• To compare the thermodynamics of substrate and redox partner binding between P450cam and CYP101D1.
• To elucidate the structural and functional differences in their binding interfaces.
• To investigate the impact of substrate binding on redox partner interaction.

Main Methods:

• Isothermal titration calorimetry (ITC) to determine binding thermodynamics.
• Molecular dynamics (MD) simulations to assess substrate stability.
• Comparative analysis of binding affinities and thermodynamic parameters.

Main Results:

• CYP101D1 binds camphor approximately 10-fold weaker than P450cam, with camphor showing less spin shift in CYP101D1.
• Camphor remains stable in the active site of CYP101D1, similar to P450cam.
• CYP101D1's ferredoxin redox partner (Arx) binds more tightly to the substrate-bound state, contrasting with P450cam's Pdx preference for the open state.
• CYP101D1-Arx binding exhibits a large negative entropy change, unlike P450cam-Pdx binding, suggesting different interfacial interactions.

Conclusions:

• CYP101D1 and P450cam display distinct substrate and redox partner binding mechanisms.
• The binding interface differences, particularly the role of Arx_L39 versus Pdx_D38, likely dictate altered binding orientations and affinities.
• These findings highlight the subtle yet significant variations in P450 enzyme function and regulation.