title: Dynamics in a pure encounter complex of two proteins studied by solution scattering and paramagnetic NMR spectroscopy.
abstract: In the general view of protein-complex formation, a transient and dynamic encounter complex proceeds to form a more stable, well-defined, and active form. In weak protein complexes, however, the encounter state can represent a significant population of the complex. The redox proteins adrenodoxin (Adx) and cytochrome c (C c) associate to form such a weak and short-lived complex, which is nevertheless active in electron transfer. To study the conformational freedom within the protein complex, the native complex has been compared to a cross-linked counterpart by using solution scattering and NMR spectroscopy. Oligomerization behavior of the native complex in solution revealed by small-angle X-ray scattering indicates a stochastic nature of complex formation. For the cross-linked complex, interprotein paramagnetic effects are observed, whereas for the native complex, extensive averaging occurs, consistent with multiple orientations of the proteins within the complex. Simulations show that C c samples about half of the surface area of adrenodoxin. It is concluded that the complex of Adx/C c is entirely dynamic and can be considered as a pure encounter complex.
authors.affiliation: Institute of Chemistry, Leiden University, P.O. Box 9502, NL-2300RA Leiden, The Netherlands.
authors.forename: Xingfu
authors.initials: X
authors.lastname: Xu
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Reinle
authors.forename: Frank
authors.initials: F
authors.lastname: Hannemann
authors.forename: Peter V
authors.initials: PV
authors.lastname: Konarev
authors.forename: Dmitri I
authors.initials: DI
authors.lastname: Svergun
authors.forename: Rita
authors.initials: R
authors.lastname: Bernhardt
authors.forename: Marcellus
authors.initials: M
authors.lastname: Ubbink
mesh_terms: D000325:Adrenodoxin / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D045304:Cytochromes c / Q000737:chemistry*; D019281:Dimerization; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D008956:Models, Chemical; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D011487:Protein Conformation; D053838:Scattering, Small Angle; D012996:Solutions; D014961:X-Ray Diffraction; D015003:Yeasts
chemical_list: D012996:Solutions; D000325:Adrenodoxin; D045304:Cytochromes c