Thermodynamic and kinetic characterization of PccH, a key protein in microbial electrosynthesis processes in Geobacter sulfurreducens

Telma C. Santos, André R. De Oliveira, Joana M. Dantas, Carlos A. Salgueiro, Cristina M. Cordas

Research output: Contribution to journalArticle

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Abstract

Abstract The monoheme c-type cytochrome PccH from Geobacter sulfurreducens, involved in the pathway of current-consumption in biofilms, was electrochemically characterized in detail. Cyclic voltammetry was used to determine the kinetics and thermodynamics properties of PccH redox behavior. Entropy, enthalpy and Gibbs free energy changes associated with the redox center transition between the ferric and the ferrous state were determined, indicating an enhanced solvent exposure. The midpoint redox potential is considerably low for a monoheme c-type cytochrome and the heterogeneous electron transfer constant rate reflects a high efficiency of electron transfer process in PccH. The midpoint redox potential dependence on the pH (redox-Bohr effect) was investigated, over the range of 2.5 to 9.1, and is described by the protonation/deprotonation events of two distinct centers in the vicinity of the heme group with pKa values of 2.7 (pKox1); 4.1 (pKred1) and 5.9 (pKox2); 6.4 (pKred2). Based on the inspection of PccH structure, these centers were assigned to heme propionic acids P13 and P17, respectively. The observed redox-Bohr effect indicates that PccH is able to thermodynamically couple electron and proton transfer in the G. sulfurreducens physiological pH range.

Original languageEnglish
Article number47485
Pages (from-to)1113-1118
Number of pages6
JournalBiochimica Et Biophysica Acta-Bioenergetics
Volume1847
Issue number10
DOIs
Publication statusPublished - Oct 2015

Keywords

  • Cytochrome
  • Electrochemistry
  • Electron transfer
  • Geobacter
  • Redox potential

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