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Updated: May 5, 2026

In Vivo Hydroxyl Radical Protein Footprinting for the Study of Protein Interactions in Caenorhabditis elegans
Published on: April 1, 2020
Hot-spot residues in the cytochrome P450cam-putidaredoxin binding interface
Yoshitaka Hiruma1, Ankur Gupta, Alexander Kloosterman
1Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, Einsteinweg 55, 2333 CC Leiden (The Netherlands).
This study investigated polar residues in the Putidaredoxin-Cytochrome P450cam (Pdx-P450cam) complex. Findings reveal these residues are crucial for partner recognition, not electron transfer efficiency.
Area of Science:
- Biochemistry
- Structural Biology
- Enzyme Kinetics
Background:
- Cytochrome P450cam (P450cam) is a key monooxygenase in camphor metabolism.
- Electron transfer to P450cam is facilitated by putidaredoxin (Pdx), a [2 Fe-2 S] cluster-containing ferredoxin.
- Recent structural data revealed novel polar residues at the Pdx-P450cam binding interface.
Purpose of the Study:
- To elucidate the energetic importance and functional role of previously unrecognized polar residues at the Pdx-P450cam interface.
- To differentiate between roles in partner recognition versus electron transfer coupling.
Main Methods:
- Site-directed mutagenesis to create specific Pdx and P450cam mutants.
- Kinetic measurements to assess electron transfer rates.
- Nuclear Magnetic Resonance (NMR) spectroscopy to probe protein interactions.
Main Results:
- Double mutant cycle (DMC) analysis identified favorable interactions between Pdx Tyr33/P450cam Asp125 and Pdx Ser42/P450cam His352.
- Alanine substitutions of several polar residues did not significantly alter electron transfer rates.
- Specific polar interactions were found to be critical for Pdx-P450cam complex formation.
Conclusions:
- Polar residues at the Pdx-P450cam interface primarily contribute to protein-protein recognition.
- These interactions are distinct from those directly mediating electronic coupling for electron transfer.
- Understanding these recognition mechanisms is vital for protein-ligand interactions in biological systems.
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