title: Crystal structure of Pseudomonas aeruginosa apo-azurin at 1.85 A resolution.
abstract: The 3D structure of apo-azurin from Pseudomonas aeruginosa has been determined at 1.85 A resolution. The crystal structure is composed of two different molecular forms of apo-azurin arranged as hetero-dimers in the tetramer of the asymmetric unit. Form 1 closely resembles the holo-protein lacking copper. Form 2 shows differences in the metal binding site region induced by the incorporation of a solvent molecule into this site. The positions of the copper ligands His46 and His117 are shifted by 0.6 A and 1.6 A. The His117 side chain adopts a position at the surface of the protein, thereby facilitating access to the copper site. The presence of two different molecular forms of apo-azurin in the crystal lattice may reflect an equilibrium between the two forms in solution. 1H-NMR spectra of apo-azurin recorded as a function of pH show that at high pH the line broadening of His35, His46 and His117 resonances is consistent with an interconversion between forms 1 and 2. At low pH, no broadening is observed. This may indicate that here the interconversion is fast on the NMR timescale.
authors.affiliation: Max Planck Institut für Biochemie, Abteilung Strukturforschung, Martinsried bei München, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Nar
authors.forename: A
authors.initials: A
authors.lastname: Messerschmidt
authors.forename: R
authors.initials: R
authors.lastname: Huber
authors.forename: M
authors.initials: M
authors.lastname: van de Kamp
authors.forename: G W
authors.initials: GW
authors.lastname: Canters
mesh_terms: D001059:Apoproteins / Q000737:chemistry*; D001400:Azurin / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011487:Protein Conformation; D011550:Pseudomonas aeruginosa / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D001059:Apoproteins; C038778:apoazurin; D001400:Azurin