Light-Induced Reduction of Bovine Adrenodoxin via the Covalently Bound Ruthenium(II) Bipyridyl Complex: Intramolecular Electron Transfer and Crystal Structure

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• 作者：Andrei Halavaty ; J&uuml ; rgen J. M&uuml ; ller ; Jö ; rg Contzen ; Christiane Jung ; Frank Hannemann ; Rita Bernhardt ; Marcus Galander ; Friedhelm Lendzian ; and Udo Heinemann
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：January 24, 2006
• 年：2006
• 卷：45
• 期：3
• 页码：709 - 718
• 全文大小：276K
• 年卷期：v.45,no.3(January 24, 2006)
• ISSN：1520-4995

文摘

Bovine adrenodoxin (Adx) plays an important role in the electron-transfer process in themitochondrial steroid hydroxylase system of the bovine adrenal cortex. Using electron paramagneticresonance (EPR) spectroscopy, we showed that photoreduction of the [2Fe-2S] cluster of Adx via (4'-methyl-2,2'-bipyridine)bis(2,2'-bipyridine)ruthenium(II) [Ru(bpy)₂(mbpy)] covalently attached to the proteinsurface can be used as a new approach to probe the "shuttle" hypothesis for the electron transfer by Adx.The 1.5 Å resolution crystal structure of a 1:1 Ru(bpy)₂(mbpy)-Adx(1-108) complex reveals the site ofmodification, Cys95, and allows to predict the possible intramolecular electron-transfer pathways withinthe complex. Photoreduction of uncoupled Adx, mutant Adx(1-108), and Ru(bpy)₂(mbpy)-Adx(1-108) using safranin T as the mediating electron donor suggests that two electrons are transferred from thedye to Adx. The intramolecular photoreduction rate constant for the ruthenated Adx has been determinedand is discussed according to the predicted pathways.