Mg2+ mediates interaction between the voltage sensor and cytosolic domain to activate BK channels.
The voltage-sensor domain (VSD) of voltage-dependent ion channels and enzymes is critical for cellular responses to membrane potential. The VSD can also be regulated by interaction with intracellular proteins and ligands, but how this occurs is poorly understood. Here, we show that the VSD of the BK-type K(+) channel is regulated by a state-dependent interaction with its own tethered cytosolic domain that depends on both intracellular Mg(2+) and the open state of the channel pore. Mg(2+) bound to the cytosolic RCK1 domain enhances VSD activation by electrostatic interaction with Arg-213 in transmembrane segment S4. Our results demonstrate that a cytosolic domain can come close enough to the VSD to regulate its activity electrostatically, thereby elucidating a mechanism of Mg(2+)-dependent activation in BK channels and suggesting a general pathway by which intracellular factors can modulate the function of voltage-dependent proteins.
Yang
Huanghe
H
Department of Biomedical Engineering and Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, MO 63130.
Hu
Lei
L
Shi
Jingyi
J
Delaloye
Kelli
K
Horrigan
Frank T
FT
Cui
Jianmin
J
D000818:Animals; D003600:Cytosol / Q000378:metabolism*; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism*; D051379:Mice; D015221:Potassium Channels / Q000502:physiology*; D055672:Static Electricity
D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D008274:Magnesium