X-ray Structure Determination and Characterization of the Pseudomonas aeruginosa Azurin Mutant Met121Glu

详细信息    查看全文

• 作者：B. Gö ; ran Karlsson ; Li-Chu Tsai ; Herbert Nar ; Joann Sanders-Loehr ; Nicklas Bonander ; Vratislav Langer ; and Lennart Sjö ; lin
• 刊名：Biochemistry
• 出版年：1997
• 出版时间：April 8, 1997
• 年：1997
• 卷：36
• 期：14
• 页码：4089 - 4095
• 全文大小：434K
• 年卷期：v.36,no.14(April 8, 1997)
• ISSN：1520-4995

文摘

The Met121Glu azurin mutant has been crystallized and thestructure determined at a resolutionof 2.3 Å. In the crystal structure a carboxyl oxygen of Met121Gluis coordinated to the metal at a distanceof 2.2 Å. Single-crystal resonance Raman spectroscopy was used toshow that the glutamic acid residuein the copper site was in the protonated state. Titration of thisresidue gives rise to a number of unusual,pH-dependent properties: as the pH is increased from 4 to 8, theS(Cys)-Cu ligand-to-metal chargetransfer bands are blue shifted and their intensity ratio is reversed,the EPR signal changes from type 1copper to a new form of protein-bound copper, and the redox potentialchanges from 370 to 180 mV.The spectroscopic changes in this pH interval are consistent witha two-state model. From the pHdependence of the optical and EPR spectra, pK_a= 5.0 for the glutamic acid in the oxidized protein wasdetermined.