STRUCTURE, FUNCTION AND REGULATION OF Na-K-ATPase

Abstract 1. 1. The Na-K-ATPase consists of a large chain (α) and a small chain (β) and possibly a proteolipid chain (γ), of molecular weights 100,000, 45,000 and about 13,000 respectively. 2. 2. Various fluorescent-labelled probes when incorporated into purified lamb kidney Na-K-ATPase, reveal important conformational changes that appear to be modified by cations, including calcium. 3. 3. The regulation ofouabain binding to the Na-K-ATPase involves interaction of both Na + and K + at an “external” site. 4. 4. Vanadate may be involved in regulation of the sodium pump, by interaction with an “internal” site. This produces modification of an “external” K + site. Both ATPase activity and ouabain binding are affected by this trace metal. 5. 5. A search is ongoing for endogenous factor(s) that specifically interact with the digitalis receptor and the Na-K-ATPase.