ISSN:
1432-1327
Keywords:
Key words Azurin
;
Cytochrome c551
;
Electron transfer
;
Site-directed mutagenesis
;
Protein crystallography
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract Replacement of the cysteine at position 112 of Pseudomonas aeruginosa azurin with an aspartic acid residue results in a mutant (Cys112Asp) protein that retains a strong copper-binding site. CuII(Cys112Asp) azurin can be reduced by excess [RuII(NH3)6]2+, resulting in a CuI protein with an electronic absorption spectrum very similar to that of wild-type CuI azurin. Cys112Asp azurin exhibits reversible interprotein electron-transfer reactivity with P. aeruginosa cytochrome c 551 (μ = 0.1 M sodium phosphate (pH 7.0);E°(CuII/I) = 180 mV vs NHE); this redox activity indicates that electrons can still enter and exit the protein through the partially solvent-exposed imidazole ring of His117. The structure of CuII(Cys112Asp) azurin at 2.4-Å resolution shows that the active-site copper is five coordinate: the pseudo-square base of the distorted square-pyramidal structure is defined by the imidazole Nδ atoms of His46 and His117 and the oxygen atoms of an asymmetrically-bound bidentate carboxylate group of Asp112; the apical position is occupied by the oxygen atom of the backbone carbonyl group of Gly45. The CuII–Asp112 interaction is distinguished by an approximately 1.2-Å displacement of the metal center from the plane defined by the Asp112 carboxylate group.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s007750050157
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