2 research outputs found
Unveiling the Structural Basis That Regulates the Energy Transduction Properties within a Family of Triheme Cytochromes from Geobacter sulfurreducens
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<sup>ā</sup>/H<sup>+</sup> transfer through the redox Bohr effect observed in
the physiological pH range, a feature not observed for cytochromes
PpcB and PpcE. In attempting to understand 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 PpcA 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 Leu<sup>6</sup> 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 form, the mutant PpcAL6F is not able to couple the
e<sup>ā</sup>/H<sup>+</sup> pathway. We carried out the reverse
mutation in PpcB and PpcE (i.e., replacing Phe<sup>6</sup> in these
two proteins by leucine) and the mutated 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 could enable the rational design of G. sulfurreducens strains that carry mutant cytochromes
with an optimal redox Bohr effect that would be suitable for various
biotechnological applications