Our research is centred upon the enzymology and crystallography of bacterial redox proteins. These include:
Enzymes of the kynurenine pathway
Tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) are heme-containing enzymes. They catalyse the oxidative cleavage of the L-Tryptophan (L-Trp) pyrrole ring. This is the first (and rate-limiting) step in L-Trp catabolism through the kynurenine pathway. We are investigating a TDO from Xanthomonas campestris and an IDO from Shewanella oneidensis and have recently obtained the first structure of reduced TDO in a binary complex with the substrate L-Trp (figure, left panel).
We have recently determined (to 2.2 Å resolution) the X-ray structure of a unique octaheme cytochrome from the bacterium Shewanella oneidensis (figure, middle panel). The protein has an unprecedented structure and we are just beginning to investigate its molecular properties. Recent results suggest the enzyme may be involved in the bacterial nitrogen cycle.
SHP and DHC
Sphaeroides heme protein (SHP) and diheme cytochrome c (DHC) (figure, right panel) have been demonstrated to be redox partners in vitro. SHP has a labile asparagine heme ligand, which is displaced from the iron upon reduction of the protein. We are currently exploring the possibility of nitric oxide dioxygenase activity in SHP via a combination of kinetic, crystallographic and phenotypic experiments
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