Structures of ruthenium-modified Pseudomonas aeruginosa azurin and [Ru(2,2′-bipyridine)2(imidazole)2]SO4•10H2O

The crystal structure of Ru(2,2'-bipyridine)(2)(imidazole) (His83)azurin (RuAz) has been determined to 2.3 Angstrom resolution by X-ray crystallography. The spectroscopic and thermodynamic properties of both the native protein and [Ru(2,2'-bipyridine)(2)(imidazole)(2)](2+) are maintained in the modified protein. Dark-green RuAz crystals grown from PEG 4000, LiNO3, CuCl2 and Tris buffer are monoclinic, belong to the space group C2 and have cell parameters a = 100.6, b = 35.4, c = 74.7 Angstrom and beta = 106.5 degrees. In addition, [Ru(2,2'-bipyridine)(2)(imidazole)(2)]SO4. 10H(2)O was synthesized, crystallized and structurally characterized by X-ray crystallography. Red-brown crystals of this complex are monoclinic, space group P2(1)/n, unit-cell parameters a = 13.230 (2), b = 18.197 (4), c=16.126(4)Angstrom, beta=108.65 (2)degrees. Stereochemical parameters for the refinement of Ru(2,2'-bipyridine),(imidazole) (His83) were taken from the atomic coordinates of [Ru(2,2'-bipyridine)(2)(imidazole)(2)](2+). The structure of RuAz confirms that His83 is the only site of chemical modification and that the native azurin structure is not perturbed significantly by the ruthenium label.