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G{beta}{gamma} and KACh: Old Story, New Insights

Dissociation of the heterotrimeric GTP-binding protein (G protein) βγ subunits from the α subunit is a prerequisite step in the ability of these proteins to signal to downstream effectors. There is evidence that ions such as Na+ and Cl- can facilitate this dissociation. Interestingly, for KACh, the first known effector for Gβγ, intracellular Na+ can also activate the channel independently of Gβγ. Both Gβγ and Na+ strengthen channel interactions with the membrane phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2), an event thought to be essential in opening the channel. PIP2 interacts with channel regions that form a binding pocket proximal to the transmembrane domains and is likely to exert a tangential, pulling force to mechanically open a gate at the cytoplasmic face of the channel pore. The tangential force generated by channel-PIP2 interactions is the likely force behind gating in all inwardly rectifying K+ channels. The gate opens when the lower part of the pore-lining transmembrane α helix pivots around a glycine residue in the middle of the helix. This mechanism of channel gating is conserved among K+ channels from bacteria to mammals and may represent a common mechanism for K+ channel gating.

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Classifications


Resource Type: Diagram, Illustration, Journal article/Issue, Review
Audience Level: Undergraduate upper division 15-16, Graduate, Professional (degree program)

Author and Copyright


Authors and Editors: Tooraj Mirshahi of Department of Physiology and Biophysics, New York University, Taihao Jin of Mt. Sinai School of Medicine, New York University, Diomedes E. Logothetis of Department of Physiology and Biophysics, New York University
Publisher: American Association for the Advancement of Science
Format: application/pdf, image/gif, image/jpeg, text/html
Copyright and other restrictions: Yes
Cost: Yes

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