Multisubstrate Allostery with a Single Helical Switch in Cytochrome P450cam

Area of Science:

• Biochemistry
• Structural Biology
• Enzyme Kinetics

Background:

• Cytochrome P450cam displays complex conformational changes and allostery.
• A unified mechanism explaining these behaviors has been lacking.

Purpose of the Study:

• To identify the key regulatory element governing P450cam conformational dynamics and allostery.
• To elucidate the mechanism of substrate-induced allosteric coupling.

Main Methods:

• Multimicrosecond molecular dynamics (MD) simulations.
• Nuclear Magnetic Resonance (NMR) pseudocontact shifts.
• Ensemble analysis of over 100 crystal structures.

Main Results:

• The I-helix (αI) acts as a master regulator, transitioning between straight and kinked states.
• Glycines G248 and G249 provide intrinsic flexibility for these transitions.
• Substrate binding stabilizes the straight αI conformation, altering solvent channels and allosteric sites.
• This mechanism explains cooperativity and resolves structural discrepancies.

Conclusions:

• The I-helix is the central switch for P450cam allostery and function.
• The G249 residue is conserved in human P450s, suggesting broad relevance.
• Engineered mutants confirm αI's role as a tunable allosteric switch.
• This provides a framework for rational P450 engineering.