Cytochrome P450cam and its complexes. Mössbauer parameters of the heme iron.
Mössbauer spectroscopy has been used to study the heme iron in various states of cytochrome P450cam from the camphor-hydroxylating system of the bacterium Pseudomonas putida. Native, camphor-free P450cam contains low-spin ferric iron, part of which (approx. 50-70%) is converted to the high-spin ferric state upon addition of camphor. The Mössbauer spectra of the camphor-free enzyme (S equals 1/2) and of the high-spin component (S equals 5/2) of the camphor complex have been successfully simulated using a model based on crystal-field theory and simple convalency considerations. The native low-spin ferric state of P450cam forms a complex with 2-phenylimidazole, with small changes in the g values and Mössbauer spectra. These changes can be accounted for consistently in the crystal-field model referred to above. The addition of putidaredoxin to the camphor-complexed, oxidized P450cam decreases the intensity of the high-spin component and changes its quadrupole splitting. The reduced form of P450cam contrins high-spin ferrous iron, both in the presence and absence of camphor. The complex of reduced P450cam with molecular oxygen is diamagnetic and has a combination of quadrupole splitting and isomer shift that is unusual for a ferrous complex, but strongly resembles that of oxyhemoglobin. These results are compatible with the bound superoxide, Fe3+-O-2, model proposed for oxyhemoglobin (Weiss, J. J. (1964) Nature 202, 83-84). Reduced P450cam and its complexes, oxyP450cam-CO, are all found to be analogous in some respects to the corresponding hemoglobin complexes.
D001665:Binding Sites; D003577:Cytochrome P-450 Enzyme System; D006418:Heme / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000032:analysis; D008433:Mathematics; D010084:Oxidation-Reduction; D011485:Protein Binding; D011487:Protein Conformation; D011549:Pseudomonas / Q000201:enzymology; D013057:Spectrum Analysis; D013696:Temperature
D006418:Heme; D003577:Cytochrome P-450 Enzyme System; D007501:Iron