Factors Influencing Redox Thermodynamics and Electron Self-Exchange for the [Fe4S4] Cluster in Chromatium vinosum High Potential Iron Protein: The Role of Core Aromatic Re

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• 作者：Aileen Soriano ; Dawei Li ; Shumin Bian ; Anshu Agarwal ; and J. A. Cowan
• 刊名：Biochemistry
• 出版年：1996
• 出版时间：September 24, 1996
• 年：1996
• 卷：35
• 期：38
• 页码：12479 - 12486
• 全文大小：474K
• 年卷期：v.35,no.38(September 24, 1996)
• ISSN：1520-4995

文摘

The roles of aromatic core residues in regulating the reductionpotential, the enthalpy andentropy of reduction, and the self-exchange rate constants forelectron-transfer reactions for the prosthetic[Fe₄S₄]^3+/2+ cluster ofChromatium vinosum high potential iron protein (HiPIP) havebeen addressed bya combination of site-directed mutagenesis, high field NMR (EXSY)experiments, and variable temperaturespectrochemical redox titration measurements. Minimal changes areobserved following nonconservativemutation of residues Tyr19, Phe48, and Phe66. Apparently thesehydrophobic residues play only a minorrole in defining the electronic properties of the cluster. Thesedata support a model, first defined fromresults obtained on Tyr19 mutant HiPIP's [Agarwal, A., Li, D., &Cowan, J. A. (1995) Proc. Natl. Acad.Sci. U.S.A. 92, 9440-9444], in which the aromaticcore restricts solvent accessibility and therebystabilizesthe oxidized [Fe₄S₄]³⁺cluster.