2n91

Publication Abstract from PubMed

A family of triheme cytochromes from Geobacter sulfurreducens plays an important role in extracellular electron transfer. In addition to their role in electron transfer pathways, two members of this family (PpcA and PpcD) were also found to be able to couple e-/H+ transfer through the redox-Bohr effect observed in the physiological pH range, a feature not observed for cytochromes PpcB and PpcE. As part of understanding the molecular control of the redox-Bohr effect in this family of cytochromes, which is highly homologous both in amino acid sequence and structures, it was observed that residue 6 is a conserved leucine in PcpA and PpcD, whereas in the other two characterized members (PpcB and PpcE) the equivalent residue is a phenylalanine. To determine the role of this residue located close to the redox-Bohr center, we replaced Leu6 in PpcA with Phe and determined the redox properties of the mutant, as well as its solution structure in the fully reduced state. In contrast with the native, the mutant PpcAL6F is not able to couple e-/H+ pathway. We carried out the reverse mutation in PpcB and PpcE (i.e., replace Phe6 in these two proteins by leucine) and show that the mutant proteins showed an increased redox-Bohr effect. The results clearly establish the role of residue 6 in the control of the redox-Bohr effect in this family of cytochromes, a feature that can enable rational design of G. sulfurreducens strains carrying mutant cytochromes with optimal redox-Bohr effect as suitable for various biotechnological applications.

Unveil the Structural Basis that Regulates the Energy Transduction Properties within a Family of Triheme Cytochromes from Geobacter sulfurreducens.,Dantas JM, Simoes T, Morgado L, Caciones C, Fernandes AP, Silva MA, Bruix M, Pokkuluri PR, Salgueiro CA J Phys Chem B. 2016 Sep 7. PMID:27603556^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.