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Structural flexibility and functional versatility of cytochrome P450 and rapid evolution
M Negishi1, M Iwasaki, R O Juvonen
1Laboratory of Reproductive and Development Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
Mutation Research
|February 19, 1996
Summary
Cytochrome P450 enzymes show diverse activities due to mutations in key residues within their heme pocket. These mutations alter substrate specificity, explaining the functional versatility of P450 proteins.
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- Cytochrome P450 (P450) enzymes are crucial heme-thiolate proteins involved in metabolizing diverse endogenous and exogenous compounds.
- P450 enzymes exhibit remarkable functional versatility, enabling the metabolism of a wide array of substrates.
Purpose of the Study:
- To investigate the molecular basis for the diverse activities and substrate specificities of cytochrome P450 enzymes.
- To identify key structural regions responsible for the functional versatility of P450s.
Main Methods:
- Site-directed mutagenesis studies to alter key residues within the P450 enzyme.
- Molecular modeling to predict the location of critical residues within the substrate-heme pocket.
- Phylogenetic analysis to examine substitution rates in substrate binding regions.
Main Results:
- A single mutation in key residues can significantly alter P450 substrate and product specificities.
- Key residues influencing P450 activity are located in the substrate-heme pocket, particularly the B' helix, F helix, and F/G loop.
- These regions exhibit high variability and rapid nonsynonymous substitution rates, leading to altered pocket geometry and diversified P450 activity.
Conclusions:
- The functional versatility of P450 enzymes is largely attributed to alterations in the substrate-binding pocket.
- Rapid mutations within specific structural regions drive the diversification of P450 activities and substrate specificities.