Chloro(2,2':6',2"-terpyridine) platinum inhibition of the renal Na+,K+-ATPase.
Ruddock, Nancy T., Krista L. Arnett, Betty Jo Wilson, and Mark A. Milanick.
Department of Physiology, School of Medicine, and Dalton Cardiovascular Research
Center, University of Missouri, Columbia, Missouri 65211
APStracts 10:0072C, 2003.
Chloro(2,2':6',2"-terpyridine) platinum, a bulky, hydrophilic reagent, inhibited the
renal sodium pump with a single exponential time course. K+ increased the rate constant
of the reaction by about twofold; the K+ concentration dependence was monotonic, with
a half-maximal effect observed at 1 mM, consistent with K+ acting at a transport site.
Na+, Mg2+, eosin, and vanadate did not significantly alter the rate of reaction. The
results of proteolysis and mass spectrometer analysis were consistent with terpyridine
platinum labeling of Cys452, Cys456, or Cys457. Because phenylarsine oxide reacts with
vicinal cysteines and did not prevent terpyridine platinum modification, terpyridine
platinum most likely modifies Cys452. This modification prevents ADP binding;
interestingly, the analogous residue in sarco(endo)plasmic reticulum Ca2+-ATPase
(SERCA) is on the exterior of the nucleotide-binding pocket. Thus it appears that the
terpyridine platinum residue is more accessible in the presence of K+ than in its absence
and that terpyridine platinum modification prevents nucleotide binding.
Received 16 March 2001; accepted in final form 23 January 2003
APS Manuscript Number C139-1.
Article publication pending Am J Physiol Cell Physiol
ISSN 1080-4757 Copyright 2003 The American Physiological Society.
Published in APStracts on 25 March 2003