Conformational and Thermodynamic Control of Electron Transfer in Neuronal Nitric Oxide Synthase

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• 作者：Adrian J. Dunford ; Stephen E. J. Rigby ; Sam Hay ; Andrew W. Munro ; Nigel S. Scrutton
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：May 1, 2007
• 年：2007
• 卷：46
• 期：17
• 页码：5018 - 5029
• 全文大小：492K
• 年卷期：v.46,no.17(May 1, 2007)
• ISSN：1520-4995

文摘

Multiple solution-state techniques have been employed in investigating the nature and controlof electron transfer in the context of the proposed "domain shuffle hypothesis" for intraprotein electrontransfer inferred from the crystal structure of the nitric oxide synthase reductase domain. NADPH analoguesand fragments have been used to map those regions of this substrate that are important in eliciting aconformational change, observed in both the fluorescence emission of the flavin cofactors of the enzymeand the EPR spectra of the FMN flavosemiquinone state. EPR and UV-visible potentiometric methodshave demonstrated a substantial calmodulin-dependent perturbation in the midpoint reduction potentialsof the redox couples of both flavin cofactors, in contrast to a previous report [Noble, M. A., et al. (1999)Biochemistry 38, 16413-16418]. These studies support a model in which FMN domain mobility, triggeredby Ca²⁺-calmodulin binding and antagonized by substrate binding, facilitates electron transfer in nitricoxide synthase through conformational change and effects a major change in the midpoint reductionpotentials of the flavin redox couples. These results are discussed in light of the recent crystal structureof the NADPH-locked reductase domain.