Open AccessPresence of a Na + ‐stimulated P‐type ATPase in the plasma membrane of the alkaliphilic halotolerant cyanobacterium Aphanothece halophytica
Author(s) -
Wiang Kanjana,
Raksajit Wuttinun,
Incharoensakdi Aran
Publication year - 2007
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2007.00667.x
Subject(s) - monensin , protonophore , antiporter , atpase , ionophore , chemistry , nigericin , ouabain , valinomycin , oligomycin , amiloride , sodium , membrane , biochemistry , enzyme , organic chemistry
Aphanothece cells could take up Na + and this uptake was strongly inhibited by the protonophore, carbonyl cyanide m ‐chlorophenylhydrazone (CCCP). Cells preloaded with Na + exhibited Na + extrusion ability upon energizing with glucose. Na + was also taken up by the plasma membranes supplied with ATP and the uptake was abolished by gramicidin D, monensin or Na + ‐ionophore. Orthovanadate and CCCP strongly inhibited Na + uptake, whereas N , N′ ‐dicyclohexylcarbodiimide (DCCD) slightly inhibited the uptake. Plasma membranes could hydrolyse ATP in the presence of Na + but not with K + , Ca 2+ and Li + . The K m values for ATP and Na + were 1.66±0.12 and 25.0±1.8 mM, respectively, whereas the V max value was 0.66±0.05 μmol min −1 mg −1 . Mg 2+ was required for ATPase activity whose optimal pH was 7.5. The ATPase was insensitive to N ‐ethylmaleimide, nitrate, thiocyanate, azide and ouabain, but was substantially inhibited by orthovanadate and DCCD. Amiloride, a Na + /H + antiporter inhibitor, and CCCP showed little or no effect. Gramicidin D and monensin stimulated ATPase activity. All these results suggest the existence of a P‐type Na + ‐stimulated ATPase in Aphanothece halophytica . Plasma membranes from cells grown under salt stress condition showed higher ATPase activity than those from cells grown under nonstress condition.