Open AccessA cation/proton antiport activity in Acholeplasma laidlawii
Author(s) -
Lelong I.,
Shirvan M.H.,
Rottem S.
Publication year - 1989
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.1574-6968.1989.tb03085.x
Subject(s) - acridine orange , vesicle , antiporter , chemistry , lysis , membrane , efflux , biochemistry , biophysics , biology , apoptosis
Sealed membrane vesicles of Acholeplasma laidlawii were obtained by controlled lysis of carotenoid‐rich intact cells. An imposed ΔpH was created by loading membrane vesicles or intact Acholeplasma laidlawii cells with 0.25 M NH 4 Cl and diluting them into 0.25 M choline chloride. The passive efflux of NH 3 from the membrane vesicles or cells resulted in the creation of a ΔpH (inside acid) that could be visualized by the quenching of the fluorescence of the weak base acridine orange. Whereas with isolated membrane vesicles, the fluorescence was dequenched by the addition of Na + , with intact cells, K + ín addition to Na + was required. These results strongly suggest a Na + /H + exchange activity that in intact Acholeplasma laidlawii cells is K + ‐dependent. The possible role of the Na + /H + exchange activity in pH homeostasis at the more alkaline pH range, as well as in the extrusion of excess Na + from the cells is discussed.