Abstract
To determine the mechanism of nucleotide-dependent, Na+-stimulated binding of [3H]-ouabain to (Na+ + K+)-ATPase (EC 3.6.1.3), we tested the ability of β,γ-methylene ATP (adenylylmethylenediphosphonate) to support [3H]ouabain binding. β,γ-Methylene ATP is an analogue of ATP in which the β- and γ-phosphates are linked by a methylene group. It is not hydrolyzed by the (Na+ + K+)-ATPase. In the presence of Na+ and Mg++, β,γ-methylene ATP did not support [3H]ouabain binding to rat brain (Na+ + K+)-ATPase and it inhibited ATP-dependent binding. When [3H]ouabain binding to guinea pig kidney (Na+ + K+)-ATPase was determined in the presence of Na+, Mg++, and Pi, the addition of β,γ-methylene ATP was inhibitory, in contrast to the stimulation produced by ATP. These results show that β,γ-methylene ATP binds to the (Na+ + K+)-ATPase and that this interaction does not support [3H]ouabain binding.
ACKNOWLEDGMENT The authors would like to thank Mrs. Annie Han for excellent technical assistance.
- Copyright ©, 1973, by Academic Press, Inc.
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