Molecular geometries of the heme axial ligands from the triheme cytochrome PpcF from Geobacter metallireducens reveal a conserved heme core architecture

• Published in: Archives of biochemistry and biophysics 2022-07, Vol.723, p.109220-109220, Article 109220
• Main Authors: Ferreira, Marisa R., Fernandes, Tomás M., Turner, David L., Salgueiro, Carlos A.
• Format: Article
• Language: English
• Subjects: Bacterial Proteins - chemistry; Cytochromes - chemistry; Geobacter; Heme - metabolism; Humans; Ligands; Multiheme cytochromes; Nuclear magnetic resonance; Oxidation-Reduction; Paramagnetic redox centers
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/j.abb.2022.109220

Electroactive Geobacter bacteria can perform extracellular electron transfer and present a wide metabolic versatility. These bacteria reduce organic, toxic and radioactive compounds, and produce electric current while interacting with electrodes, making them interesting targets for numerous biotechnological applications. Their global electrochemical responses rely on an efficient interface between the inside and the cell's exterior, which is driven by the highly abundant periplasmic triheme PpcA-family cytochromes. The functional features of these cytochromes have been studied in G. sulfurreducens and G. metallireducens, and although they share a high degree of structural homology and sequence identity, their properties are quite distinct. In this work, the heme axial ligand geometries and the magnetic properties of PpcF from G. metallireducens were determined. The data obtained constitute important constraints for the determination of its solution structure in the oxidized state and indicate that the (i) heme core architecture; (ii) axial ligands geometries and (iii) magnetic properties of the cytochrome are conserved compared to the other members of the PpcA-families. Furthermore, the results also indicate that the heme arrangement is crucial to maintain an intrinsic regulation of the protein's redox properties and hence its electron transfer efficiency and functionality. •Geobacter are electroactive bacteria with proven biotechnological potential.•The cytochrome PpcF is important for electron transfer in G. metallireducens.•The heme core architecture and magnetic properties of PpcF were determined.•These features are conserved in the PpcA-family cytochromes from Geobacter.•The heme core arrangement broadens the redox range for electron transfer.