1GEI

STRUCTURAL CHARACTERIZATION OF N-BUTYL-ISOCYANIDE COMPLEXES OF CYTOCHROMES P450NOR AND P450CAM

Summary for 1GEI

• Entry DOI: 10.2210/pdb1gei/pdb
• Related: 1GEJ 1GEK 1GEM
• Descriptor: CYTOCHROME P450 55A1, PROTOPORPHYRIN IX CONTAINING FE, N-BUTYL ISOCYANIDE, ... (4 entities in total)
• Functional Keywords: cytocrome p450nor (fe-ii), isocyanide complexe form, oxidoreductase
• Biological source: Fusarium oxysporum
• Total number of polymer chains: 1
• Total formula weight: 45120.31

Authors

Lee, D.-S.,Park, S.-Y.,Yamane, K.,Shiro, Y. (deposition date: 2000-11-13, release date: 2000-11-29, Last modification date: 2023-10-25)

Primary citation

Lee, D.S.,Park, S.Y.,Yamane, K.,Obayashi, E.,Hori, H.,Shiro, Y.
Structural characterization of n-butyl-isocyanide complexes of cytochromes P450nor and P450cam.
Biochemistry, 40:2669-2677, 2001

PubMed Abstract: Alkyl-isocyanides are able to bind to both ferric and ferrous iron of the heme in cytochrome P450, and the resulting complexes exhibit characteristic optical absorption spectra. While the ferric complex gives a single Soret band at 430 nm, the ferrous complex shows double Soret bands at 430 and 450 nm. The ratio of intensities of the double Soret bands in the ferrous isocyanide complex of P450 varies, as a function of pH, ionic strength, and the origin of the enzyme. To understand the structural origin of these characteristic spectral features, we examined the crystallographic and spectrophotometric properties of the isocyanide complexes of Pseudomonas putida cytochrome P450cam and Fusarium oxysporum cytochorme P450nor, since ferrous isocyanide complex of P450cam gives a single Soret band at 453 nm, while that of P450nor gives one at 427 nm. Corresponding to the optical spectra, we observed C-N stretching of a ferrous iron-bound isocyanide at 2145 and 2116 cm(-1) for P450nor and P450cam, respectively. The crystal structures of the ferric and ferrous n-butyl isocyanide complexes of P450cam and P450nor were determined. The coordination structure of the fifth Cys thiolate was indistinguishable for the two P450s, but the coordination geometry of the isocyanide was different for the case of P450cam [d(Fe-C) = 1.86 A, angleFe-C-N = 159 degrees ] versus P450nor [d(Fe-C) = 1.85 A, angleFe-C-N = 175 degrees ]. Another difference in the structures was the chemical environment of the heme pocket. In the case of P450cam, the iron-bound isocyanide is surrounded by some hydrophobic side chains, while, for P450nor, it is surrounded by polar groups including several water molecules. On the basis of these observations, we proposed that the steric factors and/or the polarity of the environment surrounding the iron-bound isocyanide significantly effect on the resonance structure of the heme(Fe)-isocyanide moiety and that differences in these two factors are responsible for the spectral characteristics for P450s.

PubMed: 11258878
DOI: 10.1021/bi002225s

Experimental method

X-RAY DIFFRACTION (1.6 Å)