A calcium switch for the functional coupling between alpha (hslo) and beta subunits (KV,Ca beta) of maxi K channels.
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.
Meera
P
P
Dept of Anesthesiology, University of California, Los Angeles 90095-1778, USA.
Wallner
M
M
Jiang
Z
Z
Toro
L
L
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002413:Cations, Divalent; D002417:Cattle; D005260:Female; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008969:Molecular Sequence Data; D009215:Myometrium; D009865:Oocytes; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated; D017386:Sequence Homology, Amino Acid; D014982:Xenopus laevis
D002413:Cations, Divalent; C494841:KCNMA1 protein, human; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D002118:Calcium