INVESTIGADORES
GONZALEZ LEBRERO Rodolfo Martin
congresos y reuniones científicas
Título:
A model for the interaction between Rb+, ATP and Na+/K+-ATPase
Autor/es:
AJ SPIAGGI; MR. MONTES; RODOLFO M GONZÁLEZ LEBRERO; RC. ROSSI
Lugar:
Salta
Reunión:
Congreso; XXXIX Annual Meeting of the Argentinean Biophysical Society (SAB) and 3rd Latin American Protein Society Meeting; 2010
Institución organizadora:
Sociedad Argentina de Biofísica
Resumen:
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Occlusion of K+ (or its congeners Rb+
or Tl+) in the Na+/K+-ATPase occurs after K+-dependent
dephosphorylation (physiological route) or through a direct
route not related to ATPase activity.
Our results indicate that: i)
occlusion of Rb+ through the direct route, as well as its release
from the occluded states, are at least two-steps processes that can
be described by the sum of two exponential functions of time, for
every [Rb+] and [ATP] tested; ii) the fraction of Rb+ that is
occluded or released in the faster phase is enlarged by ATP; iii) the
initial rate of occlusion is directly proportional to free [Rb+] up
to 250 mM in the absence of ATP, whereas it decreases with [ATP] and
becomes an increasing sigmoidal function of free [Rb+] at [ATP] =
2000 mM; iv) the nucleotide markedly increases the initial rate and
the rate coefficients of both phases of Rb+ deocclusion; v) at
equilibrium, the direct route results in enzyme states that hold
either one or two occluded Rb+ ions even in enzymes with ATP bound;
vi) equilibrium between bound and occluded Rb+ seems to be almost
completely poised towards the latter in spite of the mentioned effect
of ATP on occlusion and deocclusion rates. Part of these results had
been previously observed in our lab1,2.
The kinetics of Rb+ occlusion and
deocclusion through the direct route in the presence of ATP are
consistent with a model that assumes that: 1) these processes can
follow two alternative and interrelated pathways associated with the
conformers E1 and E2; 2) only E2 can occlude Rb+; 3) uptake or
release of each cation involves an ordered-sequential process; and 4)
ATP can bind to E1 and E2, being its affinity for E1 much higher.
References:
1. González-Lebrero R. M., Kaufman S.
B., Montes M. R., Nørby J. G., Garrahan P. J. and Rossi, R. C., J.
Biol. Chem., 277, 5910 5921 (2002)
2. González-Lebrero R. M., Kaufman S.
B., Garrahan P. J. and Rossi, R. C., J. Biol. Chem., 277, 5922
5928 (2002)