Aiming to functionally optimize the respiratory electron-transfer chains, the properties of Geobacter can be explored through genetically engineered strains.

Geobacter species comprise a large number of different multiheme c-type cytochromes involved in the extracellular electron transfer pathways. The functional characterization of multiheme proteins is particularly complex because of the coexistence of several microstates in solution, connecting the fully reduced and oxidized states. NMR spectroscopy has been used to monitor the stepwise oxidation of each individual heme and thus to obtain information on each microstate. For the structural study of these proteins, a cost-effective isotopic labeling of the protein polypeptide chains was combined with the comparative analysis of 1H-13C HSQC (heteronuclear single-quantum correlation) NMR spectra obtained for labeled and unlabeled samples.

These new methodological approaches allowed us to study G. sulfurreducens heme proteins functionally and structurally, revealing functional mechanisms and key residues involved in their electron transfer capabilities.

Such advances can now be applied to the design of engineered heme proteins to improve the bioremediation and electricity-harvesting skills of G. sulfurreducens.

The targets that are currently under research in our laboratory are the following:

Triheme cytochromes

"Nanowire" cytochromes c

Outer membrane cytochromes

Signal transduction heme proteins