title: Pseudocontact shifts used in the restraint of the solution structures of electron transfer complexes.
abstract: The geometry of the ferricytochrome b5-ferricytochrome c complex has been analysed using long-range interprotein paramagnetic dipolar shifts. Heteronuclear filtered NMR spectra of samples containing 15N-labelled cytochrome b5 in complex with unlabelled cytochrome c allowed unambiguous assessment of pseudocontact shifts relative to diamagnetic reference states. Because pseudocontact shifts can be observed for protons as much as 20 A from the paramagnetic centre, this approach allows study of electron transfer proteins in fast exchange. Our findings provide the first physical evidence confirming hypotheses presented in previous theoretical studies. This absence of certain predicted shifts that are expected based on the best fit to a static model of the complex suggests that cytochrome b5 is more dynamic in solution than in the crystal, in agreement with molecular dynamics simulations.
authors.affiliation: Department of Pharmaceutical Sciences, University of Maryland at Baltimore, 21201, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Guiles
authors.forename: S
authors.initials: S
authors.lastname: Sarma
authors.forename: R J
authors.initials: RJ
authors.lastname: DiGate
authors.forename: D
authors.initials: D
authors.lastname: Banville
authors.forename: V J
authors.initials: VJ
authors.lastname: Basus
authors.forename: I D
authors.initials: ID
authors.lastname: Kuntz
authors.forename: L
authors.initials: L
authors.lastname: Waskell
mesh_terms: D000818:Animals; D003198:Computer Simulation; D003574:Cytochrome c Group / Q000737:chemistry* / Q000378:metabolism; D015786:Cytochromes b5 / Q000737:chemistry* / Q000378:metabolism; D004583:Electrons; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008862:Microsomes, Liver / Q000737:chemistry; D009590:Nitrogen Radioisotopes; D051381:Rats
chemical_list: D003574:Cytochrome c Group; D009590:Nitrogen Radioisotopes; D015786:Cytochromes b5