title: Mapping the interactions between flavodoxin and its physiological partners flavodoxin reductase and cobalamin-dependent methionine synthase.
abstract: Flavodoxins are electron-transfer proteins that contain the prosthetic group flavin mononucleotide. In Escherichia coli, flavodoxin is reduced by the FAD-containing protein NADPH:ferredoxin (flavodoxin) oxidoreductase; flavodoxins serve as electron donors in the reductive activation of anaerobic ribonucleotide reductase, biotin synthase, pyruvate formate lyase, and cobalamin-dependent methionine synthase. In addition, domains homologous to flavodoxin are components of the multidomain flavoproteins cytochrome P450 reductase, nitric oxide synthase, and methionine synthase reductase. Although three-dimensional structures are known for many of these proteins and domains, very little is known about the structural aspects of their interactions. We address this issue by using NMR chemical shift mapping to identify the surfaces on flavodoxin that bind flavodoxin reductase and methionine synthase. We find that these physiological partners bind to unique overlapping sites on flavodoxin, precluding the formation of ternary complexes. We infer that the flavodoxin-like domains of the cytochrome P450 reductase family form mutually exclusive complexes with their electron-donating and -accepting partners, complexes that require conformational changes for interconversion.
authors.affiliation: Biophysics Research Division and Department of Biological Chemistry, University of Michigan, Ann Arbor 48109-1055, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Hall
authors.forename: C W
authors.initials: CW
authors.lastname: Vander Kooi
authors.forename: C N
authors.initials: CN
authors.lastname: Stasik
authors.forename: S Y
authors.initials: SY
authors.lastname: Stevens
authors.forename: E R
authors.initials: ER
authors.lastname: Zuiderweg
authors.forename: R G
authors.initials: RG
authors.lastname: Matthews
mesh_terms: D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000737:chemistry / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D004926:Escherichia coli / Q000737:chemistry; D005418:Flavodoxin / Q000737:chemistry / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D011485:Protein Binding; D011487:Protein Conformation; D012436:S-Adenosylmethionine / Q000378:metabolism; D014805:Vitamin B 12 / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005418:Flavodoxin; D012436:S-Adenosylmethionine; D009247:NADH, NADPH Oxidoreductases; C116041:flavodoxin NADPH oxidoreductase; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; D014805:Vitamin B 12