Abstract
KV,Ca beta subunit dramatically increases the apparent calcium sensitivity of the alpha subunit of MaxiK channels when probed in the micromolar [Ca2+]i range. Analysis in a wide range of [Ca2+]i revealed that this functional coupling is exquisitely modulated by [Ca2+]i. Ca2+ ions switch MaxiK alpha+beta complex into a functionally coupled state at concentrations beyond resting [Ca2+]i. At [Ca2+] < or = 100 nM, MaxiK activity becomes independent of Ca2+, is purely voltage-activated, and its functional coupling with its beta subunit is released. The functional switch develops at [Ca2+]i that occur during cellular excitation, providing the molecular basis of how MaxiK channels regulate smooth muscle excitability and neurotransmitter release.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Animals
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Calcium / pharmacology
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Calcium / physiology*
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Cations, Divalent
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Cattle
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Female
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Humans
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Ion Channel Gating / drug effects
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Ion Channel Gating / physiology*
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Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
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Large-Conductance Calcium-Activated Potassium Channel beta Subunits
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Large-Conductance Calcium-Activated Potassium Channels
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Molecular Sequence Data
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Myometrium
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Oocytes
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Potassium Channels / genetics
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Potassium Channels / physiology*
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Potassium Channels, Calcium-Activated*
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Sequence Homology, Amino Acid
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Xenopus laevis
Substances
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Cations, Divalent
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KCNMA1 protein, human
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Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
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Large-Conductance Calcium-Activated Potassium Channel beta Subunits
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Large-Conductance Calcium-Activated Potassium Channels
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Potassium Channels
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Potassium Channels, Calcium-Activated
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Calcium