[Conformational transitions in Na, K-dependent ATPase].

Conformational transitions in membrane preparations of Na, K-dependent ATPase were studied by means of mono-radical and bi-radical hydrophobic spine probes. A decrease in micro-viscosity of non-polar membrane regions in Na, K-ATPase preparation was observed under the formation of phosphorylated N, K-ATPase intermediate in the presence of ATP and Na+ ions. K+-catalysed dephosphorylation of the intermediate resulted in opposite changes. Bi-radical probes of a certain chemical structure turned to be the most sensitive indicators of conformational changes in membranes of Na, K-ATPase preparation. Na+-, K+- and ATP-induced conformational transitions are blocked with suabaine, a specific inhibitor of Na, K-ATPase, with Ca2+ oligomycin and p-chloromercuric benzoate (PCMB). K+-dependent transitions are more sensitive to oligomycin and PCMB as compared with those induced by ATP and Na+. Possible mechanisms of conformational transitions in Na, K-dependent ATPase are discussed.