PMID:7657631
| Citation |
Eschenbrenner, M, Covès, J and Fontecave, M (1995) The flavin reductase activity of the flavoprotein component of sulfite reductase from Escherichia coli. A new model for the protein structure. J. Biol. Chem. 270:20550-5 |
|---|---|
| Abstract |
Sulfite reductase (SiR) from Escherichia coli has a alpha 8 beta 4 subunit structure, where alpha 8 is a flavoprotein (SiR-FP) containing both FAD and FMN as prosthetic groups. It also exhibits a NADPH:flavin oxidoreductase activity with exogenous riboflavin, FMN, and FAD serving as substrates. The flavin reductase activity may function during activation of ribonucleotide reductase or during ferrisiderophore reduction. A plasmid containing cysJ gene, coding for the alpha subunit, overexpresses flavin reductase activity by 100-fold, showing that alpha is the site of free flavin reduction. The overproducer allows a fast and simple preparation of large amounts of the flavoprotein. Kinetic studies of its flavin reductase activity demonstrates a ping-pong bisubstrate-biproduct reaction mechanism. NADP+ inhibition studies show that both substrates, NADPH and free flavins, bind to the same site. While the FAD cofactor mediates the electron transfer between NADPH and free flavins, the FMN cofactor is not essential since a FMN-depleted SiR-FP retains a large proportion of activity. In contradiction with previous reports, SiR-FP is found to contain 1.6-1.7 flavin per alpha subunit. This result, together with the sequence homology between SiR-FP and NADPH-cytochrome P-450 reductase, suggests a new model for the structure of the protein with one FMN and one FAD prosthetic group per alpha subunit. |
| Links | |
| Keywords |
Chromatography, DEAE-Cellulose; Electron Transport; Escherichia coli/enzymology; FMN Reductase; Flavin Mononucleotide/metabolism; Flavin-Adenine Dinucleotide/metabolism; Flavoproteins/chemistry; Flavoproteins/isolation & purification; Flavoproteins/metabolism; Kinetics; NADH, NADPH Oxidoreductases/chemistry; NADH, NADPH Oxidoreductases/isolation & purification; NADH, NADPH Oxidoreductases/metabolism; NADP/metabolism; NADP/pharmacology; Oxidoreductases Acting on Sulfur Group Donors/chemistry; Oxidoreductases Acting on Sulfur Group Donors/isolation & purification; Oxidoreductases Acting on Sulfur Group Donors/metabolism; Recombinant Proteins/chemistry; Recombinant Proteins/isolation & purification; Recombinant Proteins/metabolism; Spectrophotometry; Substrate Specificity |
| edit table |
Significance
You can help EcoliWiki by summarizing why this paper is useful
Useful Materials and Methods
You can help Ecoliwiki by describing the useful materials (strains, plasmids, antibodies, etc) described in this paper.
Annotations
<annotationlinks/>
EcoliWiki Links
Add links to pages that link here (e.g. gene, product, method pages)
References
See Help:References for how to manage references in EcoliWiki.