Biochemical and functional insights on the triheme cytochrome PpcA from Geobacter metallireducens

Pilar C. Portela, Tomás M. Fernandes, Joana M. Dantas, Marisa R. Ferreira, Carlos A. Salgueiro

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

G. metallireducens bacterium has highly versatile respiratory pathways that provide the microorganism an enormous potential for many biotechnological applications. However, little is known about the structural and functional properties of its electron transfer components. In this work, the periplasmic cytochrome PpcA from G. metallireducens was studied in detail for the first time using complementary biophysical techniques, including UV–visible, CD and NMR spectroscopy. The results obtained showed that PpcA contains three low-spin c-type heme groups with His-His axial coordination, a feature also observed for its homologue in G. sulfurreducens. However, despite the high sequence homology between the two cytochromes, important structural and functional differences were observed. The comparative analysis of the backbone, side chain and heme substituents NMR signals revealed differences in the relative orientation of the hemes I and III. In addition, redox titrations followed by visible spectroscopy showed that the redox potential values for PpcA from G. metallireducens (−78 and −93 mV at pH 7 and 8, respectively) are considerably less negative. Overall, this study provides biochemical and biophysical data of a key cytochrome from G. metallireducens, paving the way to understand the extracellular electron transfer mechanisms in these bacteria.

Original languageEnglish
Pages (from-to)8-16
Number of pages9
JournalArchives of Biochemistry and Biophysics
Volume644
DOIs
Publication statusPublished - 15 Apr 2018

Fingerprint

Geobacter
Cytochromes
Heme
histidylhistidine
Oxidation-Reduction
Bacteria
Electrons
Sequence Homology
Titration
Microorganisms
Nuclear magnetic resonance spectroscopy
Spectrum Analysis
Magnetic Resonance Spectroscopy
Nuclear magnetic resonance
Spectroscopy
5'-deoxy-5'-phosphonomethyladenosine phosphate

Keywords

  • Electron transfer
  • Geobacter
  • Multiheme c-type cytochrome

Cite this

Portela, Pilar C. ; Fernandes, Tomás M. ; Dantas, Joana M. ; Ferreira, Marisa R. ; Salgueiro, Carlos A. / Biochemical and functional insights on the triheme cytochrome PpcA from Geobacter metallireducens. In: Archives of Biochemistry and Biophysics. 2018 ; Vol. 644. pp. 8-16.
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Biochemical and functional insights on the triheme cytochrome PpcA from Geobacter metallireducens. / Portela, Pilar C.; Fernandes, Tomás M.; Dantas, Joana M.; Ferreira, Marisa R.; Salgueiro, Carlos A.

In: Archives of Biochemistry and Biophysics, Vol. 644, 15.04.2018, p. 8-16.

Research output: Contribution to journalArticle

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T1 - Biochemical and functional insights on the triheme cytochrome PpcA from Geobacter metallireducens

AU - Portela, Pilar C.

AU - Fernandes, Tomás M.

AU - Dantas, Joana M.

AU - Ferreira, Marisa R.

AU - Salgueiro, Carlos A.

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N2 - G. metallireducens bacterium has highly versatile respiratory pathways that provide the microorganism an enormous potential for many biotechnological applications. However, little is known about the structural and functional properties of its electron transfer components. In this work, the periplasmic cytochrome PpcA from G. metallireducens was studied in detail for the first time using complementary biophysical techniques, including UV–visible, CD and NMR spectroscopy. The results obtained showed that PpcA contains three low-spin c-type heme groups with His-His axial coordination, a feature also observed for its homologue in G. sulfurreducens. However, despite the high sequence homology between the two cytochromes, important structural and functional differences were observed. The comparative analysis of the backbone, side chain and heme substituents NMR signals revealed differences in the relative orientation of the hemes I and III. In addition, redox titrations followed by visible spectroscopy showed that the redox potential values for PpcA from G. metallireducens (−78 and −93 mV at pH 7 and 8, respectively) are considerably less negative. Overall, this study provides biochemical and biophysical data of a key cytochrome from G. metallireducens, paving the way to understand the extracellular electron transfer mechanisms in these bacteria.

AB - G. metallireducens bacterium has highly versatile respiratory pathways that provide the microorganism an enormous potential for many biotechnological applications. However, little is known about the structural and functional properties of its electron transfer components. In this work, the periplasmic cytochrome PpcA from G. metallireducens was studied in detail for the first time using complementary biophysical techniques, including UV–visible, CD and NMR spectroscopy. The results obtained showed that PpcA contains three low-spin c-type heme groups with His-His axial coordination, a feature also observed for its homologue in G. sulfurreducens. However, despite the high sequence homology between the two cytochromes, important structural and functional differences were observed. The comparative analysis of the backbone, side chain and heme substituents NMR signals revealed differences in the relative orientation of the hemes I and III. In addition, redox titrations followed by visible spectroscopy showed that the redox potential values for PpcA from G. metallireducens (−78 and −93 mV at pH 7 and 8, respectively) are considerably less negative. Overall, this study provides biochemical and biophysical data of a key cytochrome from G. metallireducens, paving the way to understand the extracellular electron transfer mechanisms in these bacteria.

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