Investigation of the Electron Transport Chain to and the Catalytic Activity of the Diheme Cytochrome c Peroxidase CcpA of Shewanella oneidensis
Investigation of the Electron Transport Chain to and the Catalytic Activity of the Diheme Cytochrome c Peroxidase CcpA of Shewanella oneidensis
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DOI：
10.1128/aem.00606-11
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发表时间：
2011-07
影响因子：
4.4
通讯作者：
Bjoern Schuetz;J. Seidel;Gunnar Sturm;O. Einsle;J. Gescher
中科院分区：
文献类型：
--
作者：
Bjoern Schuetz;J. Seidel;Gunnar Sturm;O. Einsle;J. Gescher
细菌二血红素c型细胞色素过氧化物酶（bccp）催化质周过氧化氢还原为水。希瓦氏γ变形杆菌在许多厌氧条件下产生过氧化物酶CcpA，包括异化铁还原条件。我们想了解这种蛋白质在生物体中的功能，以及它与电子传递链到铁的假定联系。对CcpA进行分离和过氧化物酶活性测定，并用x射线晶体学分析其结构构象。CcpA具有体外过氧化物酶活性，具有典型的二血红素过氧化物酶结构。在厌氧和嗜微气条件下，它的产量几乎相等。在50 mM柠檬酸铁和50 μM氧气的培养基中，CcpA的表达导致细胞具有很强的选择优势，这在野生型和ΔccpA突变细胞的竞争生长实验中被检测到，由于无标记缺失而缺乏整个CcpA基因。我们无法用CymA、MtrA或FccA直接降低CcpA，这些物质是铁和富马酸的电子传递链中的关键参与者，但我们确定了小单血红素ScyA是CymA和BCCP之间电子传递的中介。据我们所知，这是第一次详细描述到质周c型细胞色素过氧化物酶的完整电子传递链。本研究进一步报道了利用c型细胞色素建立特定电子传递链的可能性。
ABSTRACT Bacterial diheme c-type cytochrome peroxidases (BCCPs) catalyze the periplasmic reduction of hydrogen peroxide to water. The gammaproteobacterium Shewanella oneidensis produces the peroxidase CcpA under a number of anaerobic conditions, including dissimilatory iron-reducing conditions. We wanted to understand the function of this protein in the organism and its putative connection to the electron transport chain to ferric iron. CcpA was isolated and tested for peroxidase activity, and its structural conformation was analyzed by X-ray crystallography. CcpA exhibited in vitro peroxidase activity and had a structure typical of diheme peroxidases. It was produced in almost equal amounts under anaerobic and microaerophilic conditions. With 50 mM ferric citrate and 50 μM oxygen in the growth medium, CcpA expression results in a strong selective advantage for the cell, which was detected in competitive growth experiments with wild-type and ΔccpA mutant cells that lack the entire ccpA gene due to a markerless deletion. We were unable to reduce CcpA directly with CymA, MtrA, or FccA, which are known key players in the chain of electron transport to ferric iron and fumarate but identified the small monoheme ScyA as a mediator of electron transport between CymA and BCCP. To our knowledge, this is the first detailed description of a complete chain of electron transport to a periplasmic c-type cytochrome peroxidase. This study furthermore reports the possibility of establishing a specific electron transport chain using c-type cytochromes.