Exploring oxidative stress pathways in Geobacter sulfurreducens

Portela, Pilar C.; Morgado, Leonor; Silva, Marta A.; Denkhaus, Lukas; Einsle, Oliver; Salgueiro, Carlos A.

http://hdl.handle.net/10362/164359

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The recent reclassification of the strict anaerobe Geobacter sulfurreducens bacterium as aerotolerant brought attention for oxidative stress protection pathways. Although the electron transfer pathways for oxygen detoxification are not well established, evidence was obtained for the formation of a redox complex between the periplasmic triheme cytochrome PpcA and the diheme cytochrome peroxidase MacA. In the latter, the reduction of the high-potential heme triggers a conformational change that displaces the axial histidine of the low-potential heme with peroxidase activity. More recently, a possible involvement of the triheme periplasmic cytochrome family (PpcA-E) in the protection from oxidative stress in G. sulfurreducens was suggested. To evaluate this hypothesis, we investigated the electron transfer reaction and the biomolecular interaction between each PpcA-E cytochrome and MacA. Using a newly developed method that relies on the different NMR spectral signatures of the heme proteins, we directly monitored the electron transfer reaction from reduced PpcA-E cytochromes to oxidized MacA. The results obtained showed a complete electron transfer from the cytochromes to the high-potential heme of MacA. This highlights PpcA-E cytochromes’ efficient role in providing the necessary reducing power to mitigate oxidative stress situations, hence contributing to a better knowledge of oxidative stress protection pathways in G. sulfurreducens.

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This work was supported by Fundação para a Ciência e Tecnologia (FCT – Portugal) through the following grants: PTDC/BIA-BQM/4967/2020 (to CS), 2020.04717.BD (to PP), EXPL/BIA-BQM/0770/2021 (to LM), UIDP/04378/2020 and UIDB/04378/2020 (UCIBIO), LA/P/0140/2020 (Associate Laboratory i4HB), and Deutsche Forschungsgemeinschaft (CRC 1381, project ID 403222702; to OE). The NMR spectrometers are part of the National NMR Network (PTNMR) and are supported by FCT-MCTES (ROTEIRO/0031/2013 – PINFRA/22161/2016) co-funded by FEDER through COMPETE 2020, POCI, and PORL and FCT through PIDDAC. Publisher Copyright: Copyright © 2023 Portela, Morgado, Silva, Denkhaus, Einsle and Salgueiro.