Thermodynamic and functional characterization of the periplasmic triheme cytochrome PpcA from Geobacter metallireducens

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Abstract

The Geobacter metallireducens bacterium can couple the oxidation of a wide range of compounds to the reduction of several extracellular electron acceptors, including pollutants or electrode surfaces for current production in microbial fuel cells. For these reasons, G. metallireducens are of interest for practical biotechnological applications. The use of such electron acceptors relies on a mechanism that permits electrons to be transferred to the cell exterior. The cytochrome PpcA from G. metallireducens is a member of a family composed of five periplasmic triheme cytochromes, which are important to bridge the electron transfer from the cytoplasmic donors to the extracellular acceptors. Using NMR and visible spectroscopic techniques, a detailed thermodynamic characterization of PpcA was obtained, including the determination of the heme reduction potentials and their redox and redox-Bohr interactions. These parameters revealed unique features for PpcA from G. metallireducens compared with other triheme cytochromes from different microorganisms, namely the less negative heme reduction potentials and concomitant functional working potential ranges. It was also shown that the order of oxidation of the hemes is pH-independent, but the protein is designed to couple e /H + transfer exclusively at physiological pH.

Original languageEnglish
Pages (from-to)2861-2875
Number of pages15
JournalBiochemical Journal
Volume475
Issue number17
DOIs
Publication statusPublished - 14 Sep 2018

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Geobacter
Cytochromes
Thermodynamics
Heme
Electrons
Oxidation-Reduction
Bioelectric Energy Sources
Microbial fuel cells
Oxidation
Microorganisms
Bacteria
Electrodes
Nuclear magnetic resonance
5'-deoxy-5'-phosphonomethyladenosine phosphate
Proteins

Cite this

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title = "Thermodynamic and functional characterization of the periplasmic triheme cytochrome PpcA from Geobacter metallireducens",
abstract = "The Geobacter metallireducens bacterium can couple the oxidation of a wide range of compounds to the reduction of several extracellular electron acceptors, including pollutants or electrode surfaces for current production in microbial fuel cells. For these reasons, G. metallireducens are of interest for practical biotechnological applications. The use of such electron acceptors relies on a mechanism that permits electrons to be transferred to the cell exterior. The cytochrome PpcA from G. metallireducens is a member of a family composed of five periplasmic triheme cytochromes, which are important to bridge the electron transfer from the cytoplasmic donors to the extracellular acceptors. Using NMR and visible spectroscopic techniques, a detailed thermodynamic characterization of PpcA was obtained, including the determination of the heme reduction potentials and their redox and redox-Bohr interactions. These parameters revealed unique features for PpcA from G. metallireducens compared with other triheme cytochromes from different microorganisms, namely the less negative heme reduction potentials and concomitant functional working potential ranges. It was also shown that the order of oxidation of the hemes is pH-independent, but the protein is designed to couple e − /H + transfer exclusively at physiological pH.",
author = "Fernandes, {Tom{\'a}s M.} and Leonor Morgado and Salgueiro, {Carlos A.}",
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