The formate hydrogenlyase complex from Trabulsiella guamensis

• Applicant: Professor Dr. Gary Sawers, since 3/2024
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 460525112

The formate hydrogenlyase (FHL) complex is the central hydrogen (H2)-producing enzyme complex under fermentative growth conditions and detoxifies formate by oxidizing it to carbon dioxide and H2. The cytoplasmic soluble domain of five subunits comprises a formate dehydrogenase and hydrogenase reaction. It is attached to a membrane domain of further up to five subunits that belong to the cofactor-free MRP-type Na+/H+-antiporters. The close phylogenetic relationship with the proton-translocating complex I of the respiratory chain suggests a not yet understood energetic involvement in proton motive-force (pmf) generation. A variant with two membrane subunits from Escherichia coli is generally well-characterized, but the five-membrane subunit complex was not yet examined. Unlike E. coli, Trabulsiella guamensis is one of the few non-pathogenic enterobacteria that only encodes the extended membrane version, making it the ideal subject to study the FHL-2Tg complex and its physiological implications in energy conservation. Through genetic engineering of T. guamensis and heterologous expression of the FHL-2Tg coding hyf-genes in E. coli, we have already characterized its activity in the presence of protonophores and sodium ions. We found strong evidence for a coupling of H2-production to both H+ and Na+ translocation ability. We predict that the supernumerary membrane subunits allow additional energy conservation; hence this project investigates the underlying mechanism by combining genetic approaches with bioenergetic methods. Due to our extensive preliminary work, we can quickly combine in vivo and in vitro analysis to quantify the complex’s different ion translocation activities. Focussing on the physiological context with formate transport and essentiality analysis of the metabolic pathway to H2-production will expand our current understanding of fundamental principles of bacterial energy conservation.

• DFG Programme: Research Grants
• Ehemalige Antragstellerin: Dr. Constanze Pinske, until 3/2024