Abstract
The Na+/K+-ATPase (NKA; EC 3.6.1.37) or sodium pump is a vital ubiquitous membrane system regulating the ionic balance across the cell membrane and carrying the receptor for cardioactive steroids; the binding of these compounds to the receptor results in the inhibition of all ATPase and ion pump activities (7). We have shown in our previous studies that mercury binds to NKA so tightly that the universal chelating agent for metals, for instance, EDTA could not prevent mercury inhibition (2). In the present work we show how silver inhibits isolated NKA and how this effect can be modulated by free cysteine. The possible mechanism of on-off mechanism of silver inhibition of NKA is discussed in view of a possibly significant role of metal binding sites of NKA.