A unique aromatic residue modulates the redox range of a periplasmic multiheme cytochrome from Geobacter metallireducens
| Autor: | Pilar C. Portela, Marta A. Silva, Liliana R. Teixeira, Carlos A. Salgueiro |
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| Rok vydání: | 2021 |
| Předmět: |
Models
Molecular CIL Cambridge Isotope Laboratories 0301 basic medicine Cytochrome Stereochemistry Heme bioenergetics Biochemistry Redox 03 medical and health sciences chemistry.chemical_compound Protein Domains Redox titration Aromatic amino acids Molecular Biology Geobacter sulfurreducens 030102 biochemistry & molecular biology biology HSQC heteronuclear single quantum coherence Cell Biology Periplasmic space Geobacter metallireducens electron transfer biology.organism_classification NMR Kinetics cytochrome c 030104 developmental biology EXSY EXchange SpectroscopY chemistry Periplasm biology.protein Cytochromes site-directed mutagenesis Geobacter Hydrophobic and Hydrophilic Interactions Oxidation-Reduction Research Article |
| Zdroj: | The Journal of Biological Chemistry |
| ISSN: | 0021-9258 |
| DOI: | 10.1016/j.jbc.2021.100711 |
| Popis: | Geobacter bacteria are able to transfer electrons to the exterior of the cell and reduce extracellular electron acceptors including toxic/radioactive metals and electrode surfaces, with potential applications in bioremediation or electricity harvesting. The triheme c-type cytochrome PpcA from Geobacter metallireducens plays a crucial role in bridging the electron transfer from the inner to the outer membrane, ensuring an effective extracellular electron transfer. This cytochrome shares 80% identity with PpcA from Geobacter sulfurreducens, but their redox properties are markedly different, thus determining the distinctive working redox potential ranges in the two bacteria. PpcA from G. metallireducens possesses two extra aromatic amino acids (Phe-6 and Trp-45) in its hydrophobic heme core, whereas PpcA from G. sulfurreducens has a leucine and a methionine in the equivalent positions. Given the different nature of these residues in the two cytochromes, we have hypothesized that the extra aromatic amino acids could be partially responsible for the observed functional differences. In this work, we have replaced Phe-6 and Trp-45 residues by their nonaromatic counterparts in PpcA from G. sulfurreducens. Using redox titrations followed by UV–visible and NMR spectroscopy we observed that residue Trp-45 shifted the redox potential range 33% toward that of PpcA from G. sulfurreducens, whereas Phe-6 produced a negligible effect. For the first time, it is shown that the inclusion of an aromatic residue at the heme core can modulate the working redox range in abundant periplasmic proteins, paving the way to engineer bacterial strains for optimal microbial bioelectrochemical applications. |
| Databáze: | OpenAIRE |
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