Premium
Δψ‐dependent gating of Na + /H + exchange in Halobacterium halobium : a Δg̃mH + ‐driven Na + pump
Author(s) -
Konishi Tetsuya,
Murakami Naoyuki
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)81437-6
Subject(s) - antiporter , monensin , vesicle , chemistry , sodium , biophysics , sodium–hydrogen antiporter , gating , ion exchange , ion transporter , electrochemical gradient , hepes , crystallography , analytical chemistry (journal) , nuclear chemistry , chromatography , ion , membrane , biochemistry , biology , organic chemistry
Na + /H + antiporter‐mediated 22 Na + transport was studied in envelope vesicles from Halobacterium halobium by manipulating the size of each Δg̃m + component, ΔpH and Δψ, in the dark. Neither inside alkaline ΔpH nor outwardly directed ΔpNa + , nor a combination could facilitate 22 Na + extrusion from the vesicles. Likewise, Δψ up to 144 mV (inside negative) was not capable of initiating 22 Na + extrusion unless ΔpH existed. This extrusion was facilitated only when approx. 100 mV Δψ (gating potential) was superimposed on ΔpH (either 1 or 2). On the other hand, no uptake of 22 Na + took place even when both inside acidic ΔpH and inwardly directed Na + gradient were imposed with or without Δψ. Under these conditions, monensin mediated the rapid uptake of 22 Na + . The present results indicate that halobacterial Na + /H + exchange is regulated not only by a Δψ‐dependent gate but also by a certain mechanism to restrict the back flux of Na + , this making the antiporter capable of functioning as an efficient Δg̃mH + ‐driven pump for Na + in a high saline environment.