Send to

Choose Destination
Biochimie. 1996;78(8-9):706-13.

Cytochrome P450 conformation and substrate interactions as probed by CO binding kinetics.

Author information

Laboratory of Molecular Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.

Erratum in

  • Biochimie 1997;79(1):20.


The kinetics of CO binding to cytochrome P450, as measured by the flash photolysis technique, is a powerful probe of P450 structure-function relationships. The kinetics are sensitive to P450 conformation and dynamics and are modulated by P450 interactions with substrates and other components of the microsomal membrane. Application of a difference method to kinetic data analysis distinguishes the kinetic behavior of individual P450 forms in the microsomal membrane. This approach shows that substrates differentially modulate the kinetics via: 1) changes in P450 conformation/dynamics that either accelerate or reduce the binding rate; and/or 2) steric effects that reduce the rate. Both mechanisms are observed, the relative contributions of each varying in a substrate- and P450-dependent manner. In addition to microsomes, substrate interactions with individual P450s can be similarly probed using expressed P450s. Experiments with baculovirus-expressed human P450 3A4 show that this P450 consists of multiple conformers with distinct substrate specificities, an observation which provides a basis for its recognition of a wide array of structurally diverse substrates. These studies thus demonstrate the utility of CO binding kinetics in elucidating fundamental P450-substrate interactions in a biological membrane environment.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center