Dissecting the Functional Role of Key Residues in Triheme Cytochrome PpcA: A Path to Rational Design of G. sulfurreducens Strains with Enhanced Electron Transfer Capabilities
- Universidade Nova de Lisboa (FCT/UNL), Caparica (Portugal). Faculdade de Ciencias e Tecnologia. Departamento de Quımica. CQFB. Requimte
- Argonne National Lab. (ANL), Argonne, IL (United States). Biosciences Division
PpcA is the most abundant member of a family of five triheme cytochromes c7 in the bacterium Geobacter sulfurreducens (Gs) and is the most likely carrier of electrons destined for outer surface during respiration on solid metal oxides, a process that requires extracellular electron transfer. This cytochrome has the highest content of lysine residues (24%) among the family, and it was suggested to be involved in e2/H+ energy transduction processes. In the present work, we investigated the functional role of lysine residues strategically located in the vicinity of each heme group. Each lysine was replaced by glutamine or glutamic acid to evaluate the effects of a neutral or negatively charged residue in each position. The results showed that replacing Lys9 (located near heme IV), Lys18 (near heme I) or Lys22 (between hemes I and III) has essentially no effect on the redox properties of the heme groups and are probably involved in redox partner recognition. On the other hand, Lys43 (near heme IV), Lys52 (between hemes III and IV) and Lys60 (near heme III) are crucial in the regulation of the functional mechanism of PpcA, namely in the selection of microstates that allow the protein to establish preferential e2/H+ transfer pathways. The results showed that the preferred e2/H+ transfer pathways are only established when heme III is the last heme to oxidize, a feature reinforced by a higher difference between its reduction potential and that of its predecessor in the order of oxidation. We also showed that K43 and K52 mutants keep the mechanistic features of PpcA by establishing preferential e2/H+ transfer pathways at lower reduction potential values than the wild-type protein, a property that can enable rational design of Gs strains with optimized extracellular electron transfer capabilities.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER). Biological Systems Science Division
- Grant/Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1627725
- Journal Information:
- PLoS ONE, Vol. 9, Issue 8; ISSN 1932-6203
- Publisher:
- Public Library of ScienceCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Rational engineering of Geobacter sulfurreducens electron transfer components: a foundation for building improved Geobacter-based bioelectrochemical technologies
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journal | July 2015 |
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