Protein鈥揚rotein Interaction Regulates the Direction of Catalysis and Electron Transfer in a Redox Enzyme Complex

详细信息    查看全文

• 作者：Duncan G. G. McMillan ; Sophie J. Marritt ; Mackenzie A. Firer-Sherwood ; Liang Shi ; David J. Richardson ; Stephen D. Evans ; Sean J. Elliott ; Julea N. Butt ; Lars J. C. Jeuken
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：July 17, 2013
• 年：2013
• 卷：135
• 期：28
• 页码：10550-10556
• 全文大小：344K
• 年卷期：v.135,no.28(July 17, 2013)
• ISSN：1520-5126

文摘

Protein鈥損rotein interactions are well-known to regulate enzyme activity in cell signaling and metabolism. Here, we show that protein鈥損rotein interactions regulate the activity of a respiratory-chain enzyme, CymA, by changing the direction or bias of catalysis. CymA, a member of the widespread NapC/NirT superfamily, is a menaquinol-7 (MQ-7) dehydrogenase that donates electrons to several distinct terminal reductases in the versatile respiratory network of Shewanella oneidensis. We report the incorporation of CymA within solid-supported membranes that mimic the inner membrane architecture of S. oneidensis. Quartz-crystal microbalance with dissipation (QCM-D) resolved the formation of a stable complex between CymA and one of its native redox partners, flavocytochrome c₃ (Fcc₃) fumarate reductase. Cyclic voltammetry revealed that CymA alone could only reduce MQ-7, while the CymA-Fcc₃ complex catalyzed the reaction required to support anaerobic respiration, the oxidation of MQ-7. We propose that MQ-7 oxidation in CymA is limited by electron transfer to the hemes and that complex formation with Fcc₃ facilitates the electron-transfer rate along the heme redox chain. These results reveal a yet unexplored mechanism by which bacteria can regulate multibranched respiratory networks through protein鈥損rotein interactions.