Bacterial Redox Homeostasis: Roles of the ABC-Type Substrate Exporter, CydDC

Escherichia coli possesses a well-characterised terminal oxidase of the cytochrome bd class. This oxidase is critical for growth and energy conservation at low oxygen tensions and under diverse conditions of stress (eg. stationary phase, high pH, oxidative stress). In several bacteria, cytochrome bd function is required for pathogenicity. We have discovered a heterodimeric ABC-type transporter. CydDC, that is essential for assembly of functional cytochrome bd. CydDC has intriguing similarities to important eukaryotic transporters like CFTR and xenobiotic-exporting systems. We have recently shown that in E. coli this transporter exports cysteine and glutathione from the cytoplasm to the periplasm, suggesting that the role of CydDC is the establishment and or maintenance of an appropriate redox environment in the periplasm.<P>
The aims of the project are: <OL> <LI> To establish the range of metabolites that can be exported by CydDC <LI> To test the hypothesis that cysteine and or GSH export maintains both cytoplasm and periplasm in critical redox states, and investigate the consequences of external redox conditions <LI> To learn more of the mechanism by which transport is achieved by CydDC explored by available site-directed mutants in which cytochrome bd formation in impaired <LI> To study the link between GSH and NO cytotoxicity. </OL> This project has considerable potential for commercial exploitation, since CydDC-catalysed export can in principle be utilised in commercial cysteine and glutathione production.