A parallel study of eosin-fluorescence change and Rb+ occlusion in the Na+/K+-ATPase

M. R. MONTES; R. M. GONZÁLEZ-LEBRERO; P. J. GARRAHAN; R. C. ROSSI

ANN. N. Y. ACADEMY SCIEN.

NYAS

Año: 2003 vol. 986 p. 298 - 300

1749-6632

Conformational changes in Na+/K+-ATPase have been studied using Eosin-Y (eosin). This fluorescent probe binds with high affinity to the E1 form of the enzyme (Kd = 0.2 - 0.5 µM) leading to an increase in fluorescence signal, while in media with K+ fluorescence is low. Besides, in our laboratory we have developed a method that allows us to measure occlusion of the K+-congener rubidium, presumably testing the E2 form of the enzyme. The aim of this work is a comparative characterization of the kinetics of the E1 « E2 conformational transition, using both eosin-fluorescence change and Rb+-occlusion experiments. Since eosin is known to bind non-covalently to the enzyme at the high affinity binding site of ATP, we firstly explored how eosin affects the interaction between Rb+ and the Na+/K+-ATPase.