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Amiloride and harmaline are potent inhibitors of NhaB a Na + /H + antiporter from Escherichia coli
Author(s) -
Pinner Elhanan,
Padan Etana,
Schuldiner Shimon
Publication year - 1995
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(95)00364-f
Subject(s) - amiloride , antiporter , antiporters , chemistry , biochemistry , sodium , pharmacology , biology , membrane , organic chemistry
The diuretic drug amiloride is a specific inhibitor of sodium transporting proteins in several cell types. Attempts to inhibit this activity in membrane vesicles derived from various bacteria, did not yield clear results. Therefore, we tested the effect of amiloride and its derivatives on the purified Na + /H + antiporters of E. coli reconstituted in functional form in proteoliposomes. Whereas NhaA is not inhibited by amiloride, both amiloride and harmaline are potent inhibitors of NhaB with K 0.5 of 6 and 15 μM, respectively. The pattern of inhibition by amiloride derivatives is different from that reported for mammalian antiporters but similar to that reported for the Na + /H + antiporter of D. salia [Katz, A., Kleyman, T.R. and Pick, U. (1994) Biochemistry 33, 2389–2393]. Clonidine is a poor inhibitor ( K 0.5 = 200 μ M) while cimetidine had no effect on the antiporter up to concentration of 1 mM. These new potent inhibitors provide us with important tools for the study of the mechanism of action of NhaB.