External succinate and potassium ions influence Dcu dependent F O F 1 -ATPase activity and H + flux of Escherichia coli
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External succinate and potassium ions influence Dcu dependent FOF1-ATPase activity and H+ flux of Escherichia coli at different pHs G. Mikoyan 1,2 & L. Karapetyan 1,2,3 & A. Vassilian 4 & A. Trchounian 1,3 & K. Trchounian 1,2,3 Received: 17 April 2020 / Accepted: 19 July 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract During fermentation Escherichia coli transport succinate mainly via Dcu family carriers. Current paper describes the role of externally added succinate on N’N’-dicyclohexylcarbodiimide (DCCD) sensitive ATPase activity and H+ flux depending on potassium ions. At pH 7.5 in wild type membrane vesicles DCCD-sensitive ATPase activity was the same as in dcuACBD quadruple mutant. In dcuACB it was increased ~ 3.3 fold while in dcuD DCCD-sensitive ATPase activity was absent. The DCCD-sensitive H+ efflux was fully dependent on FOF1 only in dcuACB mutant. This activity depended on potassium ions and only in dcuACBD mutant DCCD-sensitive ATPase activity was stimulated ~ 3 fold. At pH 5.5 DCCD-sensitive ATPase activities were determined in dcuACB or dcuD mutants but not in wild type. Interestingly, addition of potassium ions enhanced DCCD-sensitive ATPase activity in dcuD mutant ~ 3-fold compared to wild type. In dcuD mutant ~ 3-fold higher H+ uptake was registered, compared to wild type. Taken together it can be concluded that at pH 7.5 the FOF1-activity depends on DcuACB. Moreover, DcuACB but not DcuD are working towards H+ uptake direction. DcuD contributes to H+ efflux at pH 7.5 while at pH 5.5 it affects H+ influx when external succinate is present. Keywords Succinate . FOF1-ATPase . H+ flux . pH . Dcu carriers . Escherichia coli
Introduction During fermentation Escherichia coli produce different organic acids which are transported with protons in symport mechanism (Clark 1989; Gonzalez et al. 2017). The main H+ circulation enzyme during fermentative conditions is the proton FOF1-ATPase which is considered as one of the key enzymes in bioenergetics (Boyer 1997; Trchounian 2004; Trchounian and Sawers 2014). The FOF1-ATP synthase catalyzes synthesis of ATP in the terminal step of oxidative phosphorylation
* K. Trchounian [email protected] 1
Department of Biochemistry, Microbiology and Biotechnology, Faculty of Biology, Yerevan State University, 1 A. Manoogian Str, Yerevan 0025, Armenia
2
Microbial Biotechnologies and Biofuel Innovation Center, Yerevan State University, 1 A. Manoogian Str, Yerevan 0025, Armenia
3
Scientific-Research Institute of Biology, Yerevan State University, 1 A. Manoogian Str, Yerevan 0025, Armenia
4
Department of Ecology and Nature Protection, Faculty of Biology, Yerevan State University, 1 A. Manoogian Str, Yerevan 0025, Armenia
and photophosphorylation while during fermentation FOF1 works in ATP hydrolysis mode generating proton motive force (pmf). ATP hydrolysis and synthesis occur on F1 part, whereas proton transport occurs via FO. It is well known that E. coli Fo part consists of three ab2cn subunits (Weber and Senior 2003; Junge et al.
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