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Subproject 4

Role of the formate dehydrogenase orthologue and hydrogenases in organohalide respiration by Dehalococcoides strain CBDB1

Gary Sawers (University of Halle-Wittenberg)

Species of the genus Dehalococcoides are obligate organohalide respirers that utilize molecular hydrogen as electron donor. Strain CBDB1 not only has the capacity to synthesize 5 hydrogenases, it synthesizes a highly abundant membrane protein, which has a catalytic subunit that exhibits high similarity to 'classical' formate dehydrogenases (Fdh); however, the bacterium cannot use formate as an electron donor.

Our project has the following objectives:
- To determine the physiological function of the Fdh-like enzyme in organohalide respiration
- To determine whether the Hym-type [FeFe]-hydrogenase might form a complex with complex I in the respiratory chain
- To determine the contribution of individual hydrogenases to the hydrogen metabolism of the bacterium
- To determine whether Dehalococcoides species use an unique mechanism of electron transfer through the respiratory chain: these bacteria do not appear to synthesize quinones

Respiratory electron transfer from the Fdh-like enzyme complex (A) or hydrogenases (B) to reductive dehalogenases (Rdh: represented as the blue enzyme complex). A. The route of electron transfer between the electron-donating enzyme complexes and the electron-accepting Rdh enzyme complexes, the actual electron donor to the Fdh-complex, as well as whether there is an equivalent of the 'Q-cycle' (represented by the question mark) are all unknown. B. The various Hup, Hyc and Hym hydrogenases are represented. Hym is drawn speculatively in complex with the complex I (NADH dehydrogenase) components.


Selected References:

Kublik A, Deobald D, Hartwig S, Schiffmann CL, Andrades A, von Bergen M, Sawers RG, Adrian L.
Identification of a multiprotein reductive dehalogenase complex in Dehalococcoides mccartyi strain CBDB1 suggests a protein-dependent respiratory electron transport chain obviating quinone involvement
Environ Microbiol. 2015 Dec 31., doi:10.1111/1462-2920.13200

Hartwig S, Thomas C, Krumova N, Quitzke V, Türkowsky D, Jehmlich N, Adrian L, Sawers RG
Heterologous Complementation Studies in Escherichia coli with the Hyp Accessory Protein Machinery from Chloroflexi Provide Insight into [NiFe]-Hydrogenase Large Subunit Recognition by the HypC Protein Family
Microbiol, 2015 Sep 11 (Epub ahead of print) DOI: 10.1099/mic.0.000177.


Gary Sawers group