title: The flavoprotein component of the Escherichia coli sulfite reductase can act as a cytochrome P450c17 reductase.
abstract: The flavoprotein component (SiR-FP) of the E. coli sulfite reductase was found to support 17 alpha-hydroxylation of pregnenolone in the presence of cytochrome P450c17. Half maximum activity is obtained for a 1:1 ratio of SiR-FP, expressed as monomer concentration, to P450c17. When compared to bovine NADPH-cytochrome P450 reductase, SiR-FP is about 12-15 times less efficient. P450c17 was demonstrated to interact specifically with the FMN-binding domain of the protein and the N-terminal part of SiR-FP is suspected to play a role in electron transfer. A cluster of negatively charged residues was found in SiR-FP by amino acid sequence comparison with rat cytochrome P450 reductase. These results argue in favour of the flavodoxin origin of the FMN-binding domain of SiR-FP.
authors.affiliation: Laboratoire de Chimie et Biochimie des Centres Redox Biologiques, CEA-Grenoble, DBMS/CBCRB-CNRS-Université Joseph Fourier, France.
authors.forename: M
authors.initials: M
authors.lastname: Zeghouf
authors.forename: G
authors.initials: G
authors.lastname: Defaye
authors.forename: M
authors.initials: M
authors.lastname: Fontecave
authors.forename: J
authors.initials: J
authors.lastname: Coves
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D004926:Escherichia coli / Q000201:enzymology*; D019143:Evolution, Molecular; D005486:Flavin Mononucleotide; D005418:Flavodoxin / Q000235:genetics; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D011284:Pregnenolone / Q000378:metabolism; D011485:Protein Binding; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity; D050864:Sulfite Reductase (NADPH)
chemical_list: D005418:Flavodoxin; D005420:Flavoproteins; D010446:Peptide Fragments; D011284:Pregnenolone; D005486:Flavin Mononucleotide; D013254:Steroid 17-alpha-Hydroxylase; D050862:Oxidoreductases Acting on Sulfur Group Donors; D050864:Sulfite Reductase (NADPH); C494314:sulfite reductase (NADPH), E coli