The role of Escherichia coli FhlA transcriptional activator in generation of proton motive force and F0F1-ATPase activity at pH 7.5

Escherichia coli is able to utilize the mixture of carbon sources and produce molecular hydrogen (H-2) via formate hydrogen lyase (FHL) complexes. In current work role of transcriptional activator of formate regulon FhlA in generation of fermentation end products and proton motive force, N'N'-dicyclohexylcarbodiimide (DCCD)-sensitive ATPase activity at 20 and 72 hr growth during utilization of mixture of glucose, glycerol, and formate were investigated. It was shown that in fhlA mutant specific growth rate was similar to 1.5 fold lower compared to wt, while addition of DCCD abolished the growth in fhlA but not in wt. Formate was not utilized in fhlA mutant but wt cells simultaneously utilized formate with glucose. Glycerol utilization started earlier (from 2 hr) in fhlA than in wt. The DCCD-sensitive ATPase activity in wt cells membrane vesicles increased similar to 2 fold at 72 hr and was decreased 70% in fhlA. Addition of formate in the assays increased proton ATPase activity in wt and mutant strain. FhlA absence mainly affected the Delta pH but not Delta Psi component of Delta p in the cells grown at 72 hr but not in 24 hr. The Delta p in wt cells decreased from 24 to 72 hr of growth similar to 40 mV while in fhlA mutant it was stable. Taken together, it is suggested that FhlA regulates the concentration of fermentation end products and via influencing F0F1-ATPase activity contributes to the proton motive force generation.