title: Gated electron transfers and electron pathways in azurin: a NMR dynamic study at multiple fields and temperatures.
abstract: Dynamic properties of electron transfer pathways in a small blue copper cupredoxin are explored using an extensive 15N NMR relaxation study of reduced Pseudomonas aeruginosa azurin at four magnetic fields (500-900 MHz) and at two temperatures chosen well below the melting point of the protein. Following a careful model-free analysis, several protein regions with different dynamic regimes are identified. Nanosecond time-scale mobility characterizes various residues of the hydrophobic surface patch believed to mark the natural entry point for electrons, notably the surface-exposed copper-ligand His117. These findings are consistent with a gated electron transfer process according to the "dynamic docking" model. Residues 47-49 along intramolecular pathways of electrons show rigidity that is remarkably conserved when increasing the temperature. Three different conformational exchange processes were observed in the millisecond range, one near the only disulfide bridge in the molecule and two near the copper ion. The latter two processes are consistent with previous data such as crystal structures at various pH values and NMR relaxation dispersion experiments; they may indicate an additional gated electron transfer mechanism at slower time-scales.
authors.affiliation: Swedish NMR Centre, Göteborg University, Box 465, 405 30 Göteborg, Sweden.
authors.forename: Anastasia V
authors.initials: AV
authors.lastname: Zhuravleva
authors.forename: Dmitry M
authors.initials: DM
authors.lastname: Korzhnev
authors.forename: Eriks
authors.initials: E
authors.lastname: Kupce
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Arseniev
authors.forename: Martin
authors.initials: M
authors.lastname: Billeter
authors.forename: Vladislav Yu
authors.initials: VY
authors.lastname: Orekhov
mesh_terms: D001400:Azurin / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism*; D003300:Copper / Q000378:metabolism*; D004579:Electron Transport; D004583:Electrons; D007700:Kinetics; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature; D013816:Thermodynamics
chemical_list: C050107:cupredoxin; D001400:Azurin; D003300:Copper