My interests lie in the characterisation of enzymes that contain metal cofactors, principally enzymes involved in bacterial respiration. These include soluble cytoplasmic and periplasmic proteins, integral membrane proteins as well as extracellular membrane associated proteins that interact with the environment. In collaboration with colleagues in the Centre for Molecular and Structural Biochemistry, my research combines a broad range of biological, biochemical and biophysical techniques to explore protein-protein interactions, electron transfer between cofactors and the mechanism of enzyme catalysis.

Keynote Details

Tuesday 30 June

Symposium 14: Bioenergy and bioelectricity

Selective metal reduction by the extracellular cytochromes of Shewanella oneidensis.

Shewanella oneidensis has become a model organism for the study of biological metal reduction, a promising potential application for recovery of metals from different waste streams, including electronic and mining waste.  Key to this process is a metal reducing porin-cytochrome complex called MtrCAB.  This complex allows electron transfer across the outer membrane and into the surface exposed cytochrome MtrC, which can then either directly or indirectly reduce soluble metals.  MtrC is a decaheme protein where the hemes are contained in two pentaheme domains separated by two β-barrel domains.  The first pentaheme domain accepts electrons from the outer-membrane embedded MtrAB complex, while the second is capable of reducing a range of substrates.  A redox swich formed by a cysteine disulfide controls the interaction between the two pentaheme domains, and can disrupt the electron transfer pathway, switching off substrate reduction.

Surprisingly MtrC shows specificity for metals in different oxidation states, with palladium and platinum being fully reduced, while copper and gold are only partially reduced.  This suggests that coordination geometry, in addition to redox potential, important factors during reduction of different metal ions.