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Neuron
2010 Jun 24;666:871-83. doi: 10.1016/j.neuron.2010.05.009.
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An epilepsy/dyskinesia-associated mutation enhances BK channel activation by potentiating Ca2+ sensing.
Yang J
,
Krishnamoorthy G
,
Saxena A
,
Zhang G
,
Shi J
,
Yang H
,
Delaloye K
,
Sept D
,
Cui J
.
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Ca(2+)-activated BK channels modulate neuronal activities, including spike frequency adaptation and synaptic transmission. Previous studies found that Ca(2+)-binding sites and the activation gate are spatially separated in the channel protein, but the mechanism by which Ca(2+) binding opens the gate over this distance remains unknown. By studying an Asp-to-Gly mutation (D434G) associated with human syndrome of generalized epilepsy and paroxysmal dyskinesia (GEPD), we show that a cytosolic motif immediately following the activation gate S6 helix, known as the AC region, mediates the allosteric coupling between Ca(2+) binding and channel opening. The GEPD mutation inside the AC region increases BK channel activity by enhancing this allosteric coupling. We found that Ca(2+) sensitivity is enhanced by increases in solution viscosity that reduce protein dynamics. The GEPD mutation alters such a response, suggesting that a less flexible AC region may be more effective in coupling Ca(2+) binding to channel opening.
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