Open AccessInvestigation of the Electron Transport Chain to and the Catalytic Activity of the Diheme Cytochrome c Peroxidase CcpA of Shewanella oneidensis
Author(s) -
Björn Schütz,
Julian Seidel,
Gunnar Sturm,
Oliver Einsle,
Johannes Gescher
Publication year - 2011
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.00606-11
Subject(s) - shewanella oneidensis , biochemistry , peroxidase , periplasmic space , catabolite repression , ferric , chemistry , cytochrome , cytochrome c peroxidase , electron transport chain , biology , mutant , enzyme , escherichia coli , bacteria , gene , genetics , inorganic chemistry
Bacterial dihemec -type cytochrome peroxidases (BCCPs) catalyze the periplasmic reduction of hydrogen peroxide to water. The gammaproteobacteriumShewanella 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 exhibitedin 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 entireccpA 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 periplasmicc -type cytochrome peroxidase. This study furthermore reports the possibility of establishing a specific electron transport chain usingc -type cytochromes.