NapA Na(+)/H(+) Antiporter as a Sodium Extrusion System Supplementary to the Vacuolar Na(+)-ATPase in Enterococcus
M Kawano1, K Igarashi1, M Solioz2
1a Faculty of Pharmaceutical Sciences, Chiba University.
Bioscience, Biotechnology, and Biochemistry
|July 10, 2016
Abstract:
Enterococcus hirae has two sodium extrusion systems: the NapA Na(+)/H(+) antiporter and the vacuolar Na(+)-ATPase. We found that a NapA mutant, WD4, which is deficient in Na(+)/H(+) antiporter activity, grew well in the pH range of 6 to 10 up to 200 mM sodium. This was due to active, potential-independent sodium extrusion by the Na(+)-ATPase, which was induced under these conditions. The NapA Na(+)/H(+) antiporter is thus not a prerequisite for growth of E. hirae in the presence of sodium, but plays a supplementary role in sodium extrusion at acidic pH.
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