title: Structure, electrocatalysis and dynamics of immobilized cytochrome PccH and its microperoxidase.
abstract: Geobacter sulfurreducens cells have the ability to exchange electrons with conductive materials, and the periplasmic cytochrome PccH plays an essential role in the direct electrode-to-cell electron transfer in this bacterium. It has atypically low redox potential and unique structural features that differ from those observed in other c-type cytochromes. We report surface enhanced resonance Raman spectroscopic and electrochemical characterization of the immobilized PccH, together with molecular dynamics simulations that allow for the rationalization of experimental observations. Upon attachment to electrodes functionalized with partially or fully hydrophobic self-assembled monolayers, PccH displays a distribution of native and non-native heme spin configurations, similar to those observed in horse heart cytochrome c. The native structural and thermodynamic features of PccH are preserved upon attachment mixed hydrophobic (-CH3/-NH2) surfaces, while pure -OH, -NH2and -COOH surfaces do not provide suitable platforms for its adsorption, indicating that its still unknown physiological redox partner might be membrane integrated. Neither of the employed immobilization strategies results in electrocatalytically active PccH capable of the reduction of hydrogen peroxide. Pseudoperoxidase activity is observed in immobilized microperoxidase, which is enzymatically produced from PccH and spectroscopically characterized. Further improvement of PccH microperoxidase stability is required for its application in electrochemical biosensing of hydrogen peroxide.
authors.affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República, 2780-157 Oeiras, Portugal. smilja@itqb.unl.pt celiasilveira@itqb.unl.pt and UCIBIO, REQUIMTE, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Monte de Caparica, Portugal.
authors.forename: Célia M
authors.initials: CM
authors.lastname: Silveira
authors.affiliation: Departamento de Química Inorgánica, Analítica y Química Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
authors.forename: María A
authors.identifier: http://orcid.org/0000-0001-5679-3490
authors.initials: MA
authors.lastname: Castro
authors.affiliation: UCIBIO, REQUIMTE, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Monte de Caparica, Portugal.
authors.forename: Joana M
authors.initials: JM
authors.lastname: Dantas
authors.affiliation: UCIBIO, REQUIMTE, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Monte de Caparica, Portugal.
authors.forename: Carlos
authors.identifier: http://orcid.org/0000-0003-1136-809X
authors.initials: C
authors.lastname: Salgueiro
authors.affiliation: Departamento de Química Inorgánica, Analítica y Química Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Murgida
authors.affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República, 2780-157 Oeiras, Portugal. smilja@itqb.unl.pt celiasilveira@itqb.unl.pt.
authors.forename: Smilja
authors.identifier: http://orcid.org/0000-0002-0219-6743
authors.initials: S
authors.lastname: Todorovic
mesh_terms: D000327:Adsorption; D001426:Bacterial Proteins / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism*; D004566:Electrodes; D004583:Electrons; D045302:Geobacter / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism*; D013059:Spectrum Analysis, Raman; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D045304:Cytochromes c; D010544:Peroxidases; C021799:microperoxidase