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Submicromolar Ag + increases passive Na + permeability and inhibits the respiration‐supported formation of Na + gradient in Bacillus FTU vesicles
Author(s) -
Semeykina Anna L.,
Skulachev Vladimr P.
Publication year - 1990
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(90)81120-d
Subject(s) - chemistry , respiration , permeability (electromagnetism) , vesicle , biophysics , nuclear chemistry , biochemistry , membrane , biology , anatomy
The effect of Ag + on Na + pumping by Na + ‐motive NADH‐quinone reductase and terminal oxidase has been studied in Bacillus FTU inside‐out vesicles. Very low concentrations of Ag + (C= 1 × 10 −8 M or 2 × 10 −12 g ion · mg protein −1 ) are shown to inhibit the uphill Na + uptake coupled to the oxidation of NADH by fumarate or of ascorbate + TMPD by oxygen but exert no effect on the H + uptake by the H + ‐motive respiratory chain. Low Ag + also induces a specific increase in the Na + permeability of the vesicles. HQNO, added before and not after Ag + , prevents the Ag + ‐induced permeability increase, with effective HQNO concentrations being similar to those inhibiting the uphill Na + ‐uptake coupled to the NADH‐fumarate oxidoreduction. Reduction of terminal oxidase by ascorbate + TMPD in the presence of cyanide sensitizes the Na + permeability to Ag + . It is suggested that low [Ag + ], known as a specific inhibitor of electron transport by the Na + ‐motive NADH‐quinone reductase, uncouples the electron and Na + transports so that the Ag + ‐modified NADH‐quinone reductase operates as an Na + channel rather than an Na + pump. This effect is discussed in connection with the antibacterial action of Ag + .