title: DEER distance measurement between a spin label and a native FAD semiquinone in electron transfer flavoprotein.
abstract: The human mitochondrial electron transfer flavoprotein (ETF) accepts electrons from at least 10 different flavoprotein dehydrogenases and transfers electrons to a single electron acceptor in the inner membrane. Paracoccus denitrificans ETF has the identical function, shares the same three-dimensional structure and functional domains, and exhibits the same conformational mobility. It has been proposed that the mobility of the alphaII domain permits the promiscuous behavior of ETF with respect to a variety of redox partners. Double electron-electron resonance (DEER) measurements between a spin label and an enzymatically reduced flavin adenine dinucleotide (FAD) cofactor in P. denitrificans ETF gave two distributions of distances: a major component centered at 4.2 +/- 0.1 nm and a minor component centered at 5.1 +/- 0.2 nm. Both components had widths of approximately 0.3 nm. A distance of 4.1 nm was calculated using the crystal structure of P. denitrificans ETF, which agrees with the major component obtained from the DEER measurement. The observation of a second distribution suggests that ETF, in the absence of substrate, adopts some conformations that are intermediate between the predominant free and substrate-bound states.
authors.affiliation: Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Swanson
authors.forename: Velavan
authors.initials: V
authors.lastname: Kathirvelu
authors.forename: Tomas
authors.initials: T
authors.lastname: Majtan
authors.forename: Frank E
authors.initials: FE
authors.lastname: Frerman
authors.forename: Gareth R
authors.initials: GR
authors.lastname: Eaton
authors.forename: Sandra S
authors.initials: SS
authors.lastname: Eaton
mesh_terms: D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D044927:Electron-Transferring Flavoproteins / Q000737:chemistry*; D005182:Flavin-Adenine Dinucleotide; D006801:Humans; D011487:Protein Conformation; D011809:Quinones; D013113:Spin Labels
chemical_list: D044927:Electron-Transferring Flavoproteins; D011809:Quinones; D013113:Spin Labels; D005182:Flavin-Adenine Dinucleotide