IQUIFIB   02644
INSTITUTO DE QUIMICA Y FISICOQUIMICA BIOLOGICAS "PROF. ALEJANDRO C. PALADINI"
Unidad Ejecutora - UE
artículos
Título:
Alternative cycling modes of the Na/K-ATPase in the presence of either Na+ or Rb+.
Autor/es:
JOSÉ LUIS MONTI; MONTES MÓNICA RAQUEL; ROSSI ROLANDO
Revista:
BIOCHIMICA AND BIOPHYSICA ACTA
Editorial:
Elsevier
Referencias:
Año: 2013 vol. 1828 p. 1374 - 1383
ISSN:
0006-3002
Resumen:
This work is part of a more comprehensive study of the global functioning of the pump, which is aimed at validating the ping-pong nature of the transport of Na+ and K+. Such study of the physiological cycling mode of the enzyme requires dissecting the incidence of alternative cycling modes into the determinations performed. With this aim, we used membrane fragments containing pig-kidney Na+/K+-ATPase to perform measurements at 25ºC and pH=7.4 of: 1) ATPase activity and steady state levels of intermediates containing occluded Rb+, a K+ congener, at different [Rb+] in media lacking Na+, and 2) ATPase activity and steady state levels of phosphorylated intermediates at different [Na+] in media lacking Rb+. Most relevant results are: 1) Rb+ can be occluded through an ATPasic cycling mode that takes place in the absence of Na+ ions; 2) the kinetic behavior of the phosphoenzyme formed by ATP in the absence of Na+ is different from the one that is formed with Na+; 3) binding of Na+ to transport sites during catalysis is not at random unless rapid equilibrium holds.