Allosteric inhibition of the Ca2+-activated hydrophilic channel of the mitochondrial inner membrane by nucleotides
- 1 October 1980
- journal article
- research article
- Published by Springer Nature in The Journal of Membrane Biology
- Vol. 54 (3) , 231-236
- https://doi.org/10.1007/bf01870239
Abstract
The control by nucleotides of the Ca2+-activated channel which regulates the nonspecific permeability of the mitochondrial inner membrane has been investigated quantitatively. The cooperative binding of two molecules of ADP to the internal (matrix) side of the channel causes a mixed-type inhibition of channel activity. ATP, AMP, cAMP and GDP are all ineffective. NADH shows a pattern of inhibition similar to that of ADP, though the apparentK I is higher by a factor of 200. NADPH relieves the inhibition by NADH. NAD+ also inhibits, but its affinity is a factor of 10 less than that of NADH. When ADP and NADH are added together, they act synergistically to inhibit the Ca2+-activated channel. It is concluded that the concept of the modification of enzyme activity by the allosteric binding of nucleotides, which is well established for soluble enzyme systems, also has application to the regulation of channels that control membrane permeability.Keywords
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