Molecular interaction studies revealed the bifunctional behavior of triheme cytochrome PpcA from Geobacter sulfurreducens toward the redox active analog of humic substances

Joana M. Dantas, Oleksandr Kokhan, P. Raj Pokkuluri, Carlos A. Salgueiro

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Abstract Humic substances (HS) constitute a significant fraction of natural organic matter in terrestrial and aquatic environments and can act as terminal electron acceptors in anaerobic microbial respiration. Geobacter sulfurreducens has a remarkable respiratory versatility and can utilize the HS analog anthraquinone-2,6-disulfonate (AQDS) as a terminal electron acceptor or its reduced form (AH2QDS) as an electron donor. Previous studies set the triheme cytochrome PpcA as a key component for HS respiration in G. sulfurreducens, but the process is far from fully understood. In this work, NMR chemical shift perturbation measurements were used to map the interaction region between PpcA and AH2QDS, and to measure their binding affinity. The results showed that the AH2QDS binds reversibly to the more solvent exposed edge of PpcA heme IV. The NMR and visible spectroscopies coupled to redox measurements were used to determine the thermodynamic parameters of the PpcA:quinol complex. The higher reduction potential of heme IV (- 127 mV) compared to that of AH2QDS (- 184 mV) explains why the electron transfer is more favorable in the case of reduction of the cytochrome by the quinol. The clear evidence obtained for the formation of an electron transfer complex between AH2QDS and PpcA, combined with the fact that the protein also formed a redox complex with AQDS, revealed for the first time the bifunctional behavior of PpcA toward an analog of the HS. Such behavior might confer selective advantage to G. sulfurreducens, which can utilize the HS in any redox state available in the environment for its metabolic needs.

Original languageEnglish
Article number47484
Pages (from-to)1129-1138
Number of pages10
JournalBiochimica Et Biophysica Acta-Bioenergetics
Volume1847
Issue number10
DOIs
Publication statusPublished - 27 Jun 2015

Fingerprint

Geobacter
Humic Substances
Molecular interactions
Cytochromes
Oxidation-Reduction
Electrons
Hydroquinones
Heme
Respiration
Nuclear magnetic resonance
Chemical shift
Thermodynamics
Biological materials
5'-deoxy-5'-phosphonomethyladenosine phosphate
Magnetic Resonance Spectroscopy
Spectroscopy

Keywords

  • Electron transfer
  • Geobacter
  • Humics
  • Multiheme cytochromes
  • NMR

Cite this

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title = "Molecular interaction studies revealed the bifunctional behavior of triheme cytochrome PpcA from Geobacter sulfurreducens toward the redox active analog of humic substances",
abstract = "Abstract Humic substances (HS) constitute a significant fraction of natural organic matter in terrestrial and aquatic environments and can act as terminal electron acceptors in anaerobic microbial respiration. Geobacter sulfurreducens has a remarkable respiratory versatility and can utilize the HS analog anthraquinone-2,6-disulfonate (AQDS) as a terminal electron acceptor or its reduced form (AH2QDS) as an electron donor. Previous studies set the triheme cytochrome PpcA as a key component for HS respiration in G. sulfurreducens, but the process is far from fully understood. In this work, NMR chemical shift perturbation measurements were used to map the interaction region between PpcA and AH2QDS, and to measure their binding affinity. The results showed that the AH2QDS binds reversibly to the more solvent exposed edge of PpcA heme IV. The NMR and visible spectroscopies coupled to redox measurements were used to determine the thermodynamic parameters of the PpcA:quinol complex. The higher reduction potential of heme IV (- 127 mV) compared to that of AH2QDS (- 184 mV) explains why the electron transfer is more favorable in the case of reduction of the cytochrome by the quinol. The clear evidence obtained for the formation of an electron transfer complex between AH2QDS and PpcA, combined with the fact that the protein also formed a redox complex with AQDS, revealed for the first time the bifunctional behavior of PpcA toward an analog of the HS. Such behavior might confer selective advantage to G. sulfurreducens, which can utilize the HS in any redox state available in the environment for its metabolic needs.",
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Molecular interaction studies revealed the bifunctional behavior of triheme cytochrome PpcA from Geobacter sulfurreducens toward the redox active analog of humic substances. / Dantas, Joana M.; Kokhan, Oleksandr; Pokkuluri, P. Raj; Salgueiro, Carlos A.

In: Biochimica Et Biophysica Acta-Bioenergetics, Vol. 1847, No. 10, 47484, 27.06.2015, p. 1129-1138.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Molecular interaction studies revealed the bifunctional behavior of triheme cytochrome PpcA from Geobacter sulfurreducens toward the redox active analog of humic substances

AU - Dantas, Joana M.

AU - Kokhan, Oleksandr

AU - Pokkuluri, P. Raj

AU - Salgueiro, Carlos A.

N1 - Sem PDF

PY - 2015/6/27

Y1 - 2015/6/27

N2 - Abstract Humic substances (HS) constitute a significant fraction of natural organic matter in terrestrial and aquatic environments and can act as terminal electron acceptors in anaerobic microbial respiration. Geobacter sulfurreducens has a remarkable respiratory versatility and can utilize the HS analog anthraquinone-2,6-disulfonate (AQDS) as a terminal electron acceptor or its reduced form (AH2QDS) as an electron donor. Previous studies set the triheme cytochrome PpcA as a key component for HS respiration in G. sulfurreducens, but the process is far from fully understood. In this work, NMR chemical shift perturbation measurements were used to map the interaction region between PpcA and AH2QDS, and to measure their binding affinity. The results showed that the AH2QDS binds reversibly to the more solvent exposed edge of PpcA heme IV. The NMR and visible spectroscopies coupled to redox measurements were used to determine the thermodynamic parameters of the PpcA:quinol complex. The higher reduction potential of heme IV (- 127 mV) compared to that of AH2QDS (- 184 mV) explains why the electron transfer is more favorable in the case of reduction of the cytochrome by the quinol. The clear evidence obtained for the formation of an electron transfer complex between AH2QDS and PpcA, combined with the fact that the protein also formed a redox complex with AQDS, revealed for the first time the bifunctional behavior of PpcA toward an analog of the HS. Such behavior might confer selective advantage to G. sulfurreducens, which can utilize the HS in any redox state available in the environment for its metabolic needs.

AB - Abstract Humic substances (HS) constitute a significant fraction of natural organic matter in terrestrial and aquatic environments and can act as terminal electron acceptors in anaerobic microbial respiration. Geobacter sulfurreducens has a remarkable respiratory versatility and can utilize the HS analog anthraquinone-2,6-disulfonate (AQDS) as a terminal electron acceptor or its reduced form (AH2QDS) as an electron donor. Previous studies set the triheme cytochrome PpcA as a key component for HS respiration in G. sulfurreducens, but the process is far from fully understood. In this work, NMR chemical shift perturbation measurements were used to map the interaction region between PpcA and AH2QDS, and to measure their binding affinity. The results showed that the AH2QDS binds reversibly to the more solvent exposed edge of PpcA heme IV. The NMR and visible spectroscopies coupled to redox measurements were used to determine the thermodynamic parameters of the PpcA:quinol complex. The higher reduction potential of heme IV (- 127 mV) compared to that of AH2QDS (- 184 mV) explains why the electron transfer is more favorable in the case of reduction of the cytochrome by the quinol. The clear evidence obtained for the formation of an electron transfer complex between AH2QDS and PpcA, combined with the fact that the protein also formed a redox complex with AQDS, revealed for the first time the bifunctional behavior of PpcA toward an analog of the HS. Such behavior might confer selective advantage to G. sulfurreducens, which can utilize the HS in any redox state available in the environment for its metabolic needs.

KW - Electron transfer

KW - Geobacter

KW - Humics

KW - Multiheme cytochromes

KW - NMR

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M3 - Article

VL - 1847

SP - 1129

EP - 1138

JO - Biochimica Et Biophysica Acta-Bioenergetics

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SN - 0005-2728

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