Redox Partner Recognition and Selectivity of Cytochrome P450terp (CYP108A1)

Area of Science:

• Biochemistry
• Structural Biology
• Enzyme kinetics

Background:

• Cytochrome P450 (P450) enzymes catalyze essential biological reactions requiring electron transfer from redox partners.
• Understanding protein-protein interactions at the interface is crucial for P450 function and selectivity.
• Cytochrome P450terp (P450terp) and its native redox partner, terpredoxin (Tdx), serve as a model system analogous to P450cam.

Purpose of the Study:

• To elucidate the structural basis of P450terp and Tdx complexation.
• To investigate the role of specific amino acid residues in mediating redox partner interactions.
• To explore how redox partner binding influences P450terp stability and catalytic activity.

Main Methods:

• X-ray crystallography to determine the structure of terpredoxin (Tdx).
• Protein-protein docking and molecular dynamics simulations to model P450terp-Tdx complexes.
• Site-directed mutagenesis (E38L variant of Tdx) to assess functional impact.
• Enzyme activity assays and oxycomplex stability measurements.

Main Results:

• The crystal structure of terpredoxin (Tdx) was determined.
• Predicted P450terp-Tdx interaction surfaces are conserved with P450cam-Pdx, but specific interactions differ.
• A key ion pair interaction (Glu38 in Tdx with Arg114 in P450terp) was identified and mutated, reducing but not eliminating activity.
• P450terp exhibited promiscuity, accepting foreign redox partners like Pdx.
• Redox partner binding correlated with the stability of the P450 oxycomplex.

Conclusions:

• Specific interfacial residues and their interactions are critical for P450terp-Tdx complex formation and function.
• While conserved interaction surfaces exist, variations in specific contacts dictate redox partner selectivity and efficiency.
• Redox partner binding modulates P450 enzyme stability, suggesting a link between interaction and catalytic competence.