title: Tuning of functional heme reduction potentials in Shewanella fumarate reductases.
abstract: The fumarate reductases from S. frigidimarina NCIMB400 and S. oneidensis MR-1 are soluble and monomeric enzymes located in the periplasm of these bacteria. These proteins display two redox active domains, one containing four c-type hemes and another containing FAD at the catalytic site. This arrangement of single-electron redox co-factors leading to multiple-electron active sites is widespread in respiratory enzymes. To investigate the properties that allow a chain of single-electron co-factors to sustain the activity of a multi-electron catalytic site, redox titrations followed by NMR and visible spectroscopies were applied to determine the microscopic thermodynamic parameters of the hemes. The results show that the redox behaviour of these fumarate reductases is similar and dominated by a strong interaction between hemes II and III. This interaction facilitates a sequential transfer of two electrons from the heme domain to FAD via heme IV.
authors.affiliation: Requimte-CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus Caparica, 2829-516 Caparica, Portugal.
authors.forename: Miguel
authors.initials: M
authors.lastname: Pessanha
authors.forename: Emma L
authors.initials: EL
authors.lastname: Rothery
authors.forename: Caroline S
authors.initials: CS
authors.lastname: Miles
authors.forename: Graeme A
authors.initials: GA
authors.lastname: Reid
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Chapman
authors.forename: Ricardo O
authors.initials: RO
authors.lastname: Louro
authors.forename: David L
authors.initials: DL
authors.lastname: Turner
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Salgueiro
authors.forename: António V
authors.initials: AV
authors.lastname: Xavier
mesh_terms: D020134:Catalytic Domain; D003574:Cytochrome c Group / Q000737:chemistry / Q000378:metabolism*; D004583:Electrons; D006418:Heme / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011485:Protein Binding; D020592:Shewanella / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D012995:Solubility; D013385:Succinate Dehydrogenase / Q000737:chemistry* / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D003574:Cytochrome c Group; D006418:Heme; C112400:flavocytochrome c3; D013385:Succinate Dehydrogenase