Atomic Resolution Crystal Structures, EXAFS, and Quantum Chemical Studies of Rusticyanin and Its Two Mutants Provide Insight into Its Unusual Properties

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• 作者：Mark L. Barrett ; Ian Harvey ; Mahesh Sundararajan ; Rajeev Surendran ; John F. Hall ; Mark J. Ellis ; Michael A. Hough ; Richard W. Strange ; Ian H. Hillier ; and S. Samar Hasnain
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：March 7, 2006
• 年：2006
• 卷：45
• 期：9
• 页码：2927 - 2939
• 全文大小：469K
• 年卷期：v.45,no.9(March 7, 2006)
• ISSN：1520-4995

文摘

Rusticyanin from the extremophile Thiobacillus ferrooxidans is a blue copper protein withunusually high redox potential and acid stability. We present the crystal structures of native rusticyaninand of its Cu site mutant His143Met at 1.27 and 1.10 Å, respectively. The very high resolution of thesestructures allows a direct comparison with EXAFS data and with quantum chemical models of the oxidizedand reduced forms of the proteins, based upon both isolated and embedded clusters and density functionaltheory (DFT) methods. We further predict the structure of the Cu(II) form of the His143Met mutantwhich has been experimentally inaccessible due to its very high redox potential. We also present metricalEXAFS data and quantum chemical calculations for the oxidized and reduced states of the Met148Glnmutant, this protein having the lowest redox potential of all currently characterized mutants of rusticyanin.These data offer new insights into the structural factors which affect the redox potential in this importantclass of proteins. Calculations successfully predict the structure and the order of redox potentials for thethree proteins. The calculated redox potential of H143M (~400 mV greater than native rusticyanin) isconsistent with the failure of readily available chemical oxidants to restore a Cu(II) species of this mutant.The structural and energetic effects of mutating the equatorial cysteine to serine, yet to be studiedexperimentally, are predicted to be considerable by our calculations.