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Title: Molecular interactions between Geobacter sulfurreducens triheme cytochromes and the redox active analogue for humic substances

We report the bacterium Geobacter sulfurreducens can transfer electrons to quinone moieties of humic substances or to anthraquinone-2,6-disulfonate (AQDS), a model for the humic acids. The reduced form of AQDS (AH 2QDS) can also be used as energy source by G. sulfurreducens. Such bidirectional utilization of humic substances confers competitive advantages to these bacteria in Fe(III) enriched environments. Previous studies have shown that the triheme cytochrome PpcA from G. sulfurreducens has a bifunctional behavior toward the humic substance analogue. It can reduce AQDS but the protein can also be reduced by AH 2QDS. Using stopped-flow kinetic measurements we were able to demonstrate that other periplasmic members of the PpcA-family in G. sulfurreducens (PpcB, PpcD and PpcE) also showed the same behavior. The extent of the electron transfer is thermodynamically controlled favoring the reduction of the cytochromes. NMR spectra recorded for 13C, 15N-enriched samples in the presence increasing amounts of AQDS showed perturbations in the chemical shift signals of the cytochromes. The chemical shift perturbations on cytochromes backbone NH and 1H heme methyl signals were used to map their interaction regions with AQDS, showing that each protein forms a low-affinity binding complex through well-defined positive surface regions in the vicinity ofmore » heme IV (PpcB, PpcD and PpcE) and I (PpcE). Docking calculations performed using NMR chemical shift perturbations allowed modeling the interactions between AQDS and each cytochrome at a molecular level. In conclusion, the results obtained provided important structural-functional relationships to rationalize the microbial respiration of humic substances in G. sulfurreducens.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [1]
  1. Universidade NOVA de Lisboa, Campus Caparica (Portugal). UCIBIO-Requimte, Departamento de Química, Faculdade de Ciências e Tecnologia
  2. Universidade Nova de Lisboa, Av. da República EAN (Portugal). Instituto de Tecnologia Química e Biológica – António Xavier and Departamento de Química, Faculdade de Ciências e Tecnologia, FCT
  3. James Madison University, Harrisonburg, VA (United States). Department of Chemistry and Biochemistry
  4. Argonne National Lab. (ANL), Argonne, IL (United States). Biosciences Division
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Biochimica et Biophysica Acta - Bioenergetics
Additional Journal Information:
Journal Volume: 1859; Journal Issue: 8; Journal ID: ISSN 0005-2728
Publisher:
Elsevier
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division; Fundacao para a Ciencia ea Tecnologia of Portugal
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Geobacter; Humic substances; AQDS; Multiheme cytochromes; NMR; Electron transfer
OSTI Identifier:
1465730

Dantas, Joana M., Ferreira, Marisa R., Catarino, Teresa, Kokhan, Oleksandr, Pokkuluri, P. Raj, and Salgueiro, Carlos A.. Molecular interactions between Geobacter sulfurreducens triheme cytochromes and the redox active analogue for humic substances. United States: N. p., Web. doi:10.1016/j.bbabio.2018.05.007.
Dantas, Joana M., Ferreira, Marisa R., Catarino, Teresa, Kokhan, Oleksandr, Pokkuluri, P. Raj, & Salgueiro, Carlos A.. Molecular interactions between Geobacter sulfurreducens triheme cytochromes and the redox active analogue for humic substances. United States. doi:10.1016/j.bbabio.2018.05.007.
Dantas, Joana M., Ferreira, Marisa R., Catarino, Teresa, Kokhan, Oleksandr, Pokkuluri, P. Raj, and Salgueiro, Carlos A.. 2018. "Molecular interactions between Geobacter sulfurreducens triheme cytochromes and the redox active analogue for humic substances". United States. doi:10.1016/j.bbabio.2018.05.007.
@article{osti_1465730,
title = {Molecular interactions between Geobacter sulfurreducens triheme cytochromes and the redox active analogue for humic substances},
author = {Dantas, Joana M. and Ferreira, Marisa R. and Catarino, Teresa and Kokhan, Oleksandr and Pokkuluri, P. Raj and Salgueiro, Carlos A.},
abstractNote = {We report the bacterium Geobacter sulfurreducens can transfer electrons to quinone moieties of humic substances or to anthraquinone-2,6-disulfonate (AQDS), a model for the humic acids. The reduced form of AQDS (AH2QDS) can also be used as energy source by G. sulfurreducens. Such bidirectional utilization of humic substances confers competitive advantages to these bacteria in Fe(III) enriched environments. Previous studies have shown that the triheme cytochrome PpcA from G. sulfurreducens has a bifunctional behavior toward the humic substance analogue. It can reduce AQDS but the protein can also be reduced by AH2QDS. Using stopped-flow kinetic measurements we were able to demonstrate that other periplasmic members of the PpcA-family in G. sulfurreducens (PpcB, PpcD and PpcE) also showed the same behavior. The extent of the electron transfer is thermodynamically controlled favoring the reduction of the cytochromes. NMR spectra recorded for 13C,15N-enriched samples in the presence increasing amounts of AQDS showed perturbations in the chemical shift signals of the cytochromes. The chemical shift perturbations on cytochromes backbone NH and 1H heme methyl signals were used to map their interaction regions with AQDS, showing that each protein forms a low-affinity binding complex through well-defined positive surface regions in the vicinity of heme IV (PpcB, PpcD and PpcE) and I (PpcE). Docking calculations performed using NMR chemical shift perturbations allowed modeling the interactions between AQDS and each cytochrome at a molecular level. In conclusion, the results obtained provided important structural-functional relationships to rationalize the microbial respiration of humic substances in G. sulfurreducens.},
doi = {10.1016/j.bbabio.2018.05.007},
journal = {Biochimica et Biophysica Acta - Bioenergetics},
number = 8,
volume = 1859,
place = {United States},
year = {2018},
month = {5}
}