INVESTIGADORES
ROSSI Rolando Carlos
artículos
Título:
Eosin Fluorescence Changes During Rb+ Occlusion in the Na+/K+-ATPase
Autor/es:
M. R MONTES; R. M. GONZÁLEZ-LEBRERO; P. J. GARRAHAN; R. C. ROSSI
Revista:
BIOCHEMISTRY
Editorial:
American Chemical Society
Referencias:
Año: 2006 vol. 45 p. 13093 - 13100
ISSN:
0006-2960
Resumen:
We used suspensions of partially purified Na+/K+‑ATPase
from pig kidney to compare the effects of Rb+, as a K+ congener,
on the time course and on the equilibrium values of eosin fluorescence and of Rb+
occlusion. Both set of data were collected under identical conditions in the
same enzyme preparations. The incubation media lacked ATP so that all changes led
to an equilibrium distribution between enzyme conformers with and without bound
eosin and with and without bound or occluded Rb+. Results showed
that, as Rb+ concentration was increased, the equilibrium value of
fluorescence decreased and occlusion increased along rectangular hyperbolas
with similar half-maximal values. The time courses of attainment of equilibrium
showed an initial phase which was so quick as to fall below the time resolution
of our rapid-mixing apparatus. This phase was followed by the sum of at least
two exponential functions of time. In the case of fluorescence the fast
exponential term accounted for a larger fraction of the time course than in the
case of occlusion. Comparison between experimental and simulated results
suggests that fluorescence changes express a process that is coupled to Rb+
occlusion but that is completed before occlusion reaches equilibrium.