Human CYP1A1 allelic variants: baculovirus expression and purification, hydrodynamic, spectral, and catalytical properties and their potency in the formation of all-trans-retinoic acid

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Item Type:	Article
Title:	Human CYP1A1 allelic variants: baculovirus expression and purification, hydrodynamic, spectral, and catalytical properties and their potency in the formation of all-trans-retinoic acid
Creators Name:	Chernogolov, A., Behlke, J., Schunck, W.H., Roots, I. and Schwarz, D.
Abstract:	Three human cytochrome P450 1A1 (CYP1A1) allelic variants, namely wild-type (CYP1A1.1), CYP1A1.2 (I462V), and CYP1A1.4 (T461N), were expressed as C-terminal His-tagged fusions including a thrombin cleavage site in Spodoptera frugiperda insect cells by baculovirus infection. The variants were expressed with 30-90 nmol (1.8-5.4 mg) spectrally active cytochrome P450 per one liter of culture and purified to electrophoretic homogeneity by Ni-agarose chromatography. The recombinant variants were structurally characterized by UV/Vis, ultracentrifugation, and EPR. Optical and EPR spectra showed all three variants predominantly in high spin state; moreover, EPR indicated changes in the electronic structure of the heme iron of the two mutant variants. Sedimentation equilibrium experiments demonstrated the purified variants in dimeric state in the presence of 0.2% emulgen + 0.05% cholate. Higher detergent concentration, the presence of imidazole, and cleavage of the His-tag led to monomerization. Catalytic activity of all purified variants was reconstituted with purified human NADPH-P450 reductase and dilaurylphosphatidylcholine. Enzyme kinetics of ethoxyresorufin O-deethylation revealed similar Km (≈ 0.4 μM) for all variants but slightly different Vmax values (CYP1A1.1: 4.2, CYP1A1.2: 7.0, and CYP1A1.4: 3.0 nmol/min/nmol CYP1A1). The extended C-terminus influenced the enzymatic activity only slightly. All three variants are able to produce significant amounts of all-transretinoic acid from all-trans-retinal with Vmax of 4.0, 3.3, and 5.6 nmol/min/nmol CYP1A1 and Km values of 111, 83, and 250 μM for CYP1A1.1, CYP1A1.2, and CYP1A1.4, respectively. Availability of the three purified human CYP1A1 variants should facilitate further characterization of their role in metabolism of endogenous and exogenous compounds as well as structural studies.
Keywords:	Alleles, Baculoviridae, Catalysis, Cell Line, Cytochrome P-450 CYP1A1, Electron Spin Resonance Spectroscopy, Enzymologic Gene Expression Regulation, Genetic Vectors, Isoenzymes, Polyacrylamide Gel Electrophoresis, Recombinant Proteins, Spodoptera, Time Factors, Tretinoin, Animals
Source:	Protein Expression and Purification
ISSN:	1046-5928
Publisher:	Elsevier / Academic Press
Volume:	28
Number:	2
Page Range:	259-269
Date:	April 2003
Official Publication:	https://doi.org/10.1016/S1046-5928(02)00672-1
PubMed:	View item in PubMed

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