Structure, electrocatalysis and dynamics of immobilized cytochrome PccH and its microperoxidase

MURGIDA, DANIEL H.; CASTRO, MARÍA A.; MURGIDA, DANIEL H.; CASTRO, MARÍA A.; SALGUEIRO, CARLOS; SILVEIRA, CÉLIA M.; TODOROVIC, SMILJA; SALGUEIRO, CARLOS; DANTAS, JOANA M.; SILVEIRA, CÉLIA M.; TODOROVIC, SMILJA; DANTAS, JOANA M.

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Año: 2017 vol. 19 p. 8908 - 8918

1463-9076

Geobacter sulfurreducens cells have the ability to exchange electrons with conductive materials, and theperiplasmic cytochrome PccH plays an essential role in the direct electrode-to-cell electron transfer inthis bacterium. It has atypically low redox potential and unique structural features that differ from thoseobserved in other c-type cytochromes. We report surface enhanced resonance Raman spectroscopicand electrochemical characterization of the immobilized PccH, together with molecular dynamicssimulations that allow for the rationalization of experimental observations. Upon attachment to electrodesfunctionalized with partially or fully hydrophobic self-assembled monolayers, PccH displays a distributionof 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 mixedhydrophobic (?CH3/?NH2) surfaces, while pure ?OH, ?NH2 and ?COOH surfaces do not provide suitableplatforms for its adsorption, indicating that its still unknown physiological redox partner might bemembrane integrated. Neither of the employed immobilization strategies results in electrocatalyticallyactive PccH capable of the reduction of hydrogen peroxide. Pseudoperoxidase activity is observed inimmobilized microperoxidase, which is enzymatically produced from PccH and spectroscopically characterized.Further improvement of PccH microperoxidase stability is required for its application in electrochemicalbiosensing of hydrogen peroxide.