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Publication Abstract from PubMed

The Met121Glu azurin mutant has been crystallized and the structure determined at a resolution of 2.3 A. In the crystal structure a carboxyl oxygen of Met121Glu is coordinated to the metal at a distance of 2.2 A. Single-crystal resonance Raman spectroscopy was used to show that the glutamic acid residue in the copper site was in the protonated state. Titration of this residue gives rise to a number of unusual, pH-dependent properties: as the pH is increased from 4 to 8, the S(Cys)-Cu ligand-to-metal charge transfer bands are blue shifted and their intensity ratio is reversed, the EPR signal changes from type 1 copper to a new form of protein-bound copper, and the redox potential changes from 370 to 180 mV. The spectroscopic changes in this pH interval are consistent with a two-state model. From the pH dependence of the optical and EPR spectra, pKa = 5.0 for the glutamic acid in the oxidized protein was determined.

X-ray structure determination and characterization of the Pseudomonas aeruginosa azurin mutant Met121Glu.,Karlsson BG, Tsai LC, Nar H, Sanders-Loehr J, Bonander N, Langer V, Sjolin L Biochemistry. 1997 Apr 8;36(14):4089-95. PMID:9100002^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.