Send to:

Choose Destination
See comment in PubMed Commons below
Proc Natl Acad Sci U S A. 2000 May 9;97(10):5562-7.

A neuronal beta subunit (KCNMB4) makes the large conductance, voltage- and Ca2+-activated K+ channel resistant to charybdotoxin and iberiotoxin.

Author information

  • 1Department of Anesthesiology, Brain Research Institute, University of California, Los Angeles, CA 90095-7115, USA.


Large conductance voltage and Ca(2+)-activated K(+) (MaxiK) channels couple intracellular Ca(2+) with cellular excitability. They are composed of a pore-forming alpha subunit and modulatory beta subunits. The pore blockers charybdotoxin (CTx) and iberiotoxin (IbTx), at nanomolar concentrations, have been invaluable in unraveling MaxiK channel physiological role in vertebrates. However in mammalian brain, CTx-insensitive MaxiK channels have been described [Reinhart, P. H., Chung, S. & Levitan, I. B. (1989) Neuron 2, 1031-1041], but their molecular basis is unknown. Here we report a human MaxiK channel beta-subunit (beta4), highly expressed in brain, which renders the MaxiK channel alpha-subunit resistant to nanomolar concentrations of CTx and IbTx. The resistance of MaxiK channel to toxin block, a phenotype conferred by the beta4 extracellular loop, results from a dramatic ( approximately 1,000 fold) slowdown of the toxin association. However once bound, the toxin block is apparently irreversible. Thus, unusually high toxin concentrations and long exposure times are necessary to determine the role of "CTx/IbTx-insensitive" MaxiK channels formed by alpha + beta4 subunits.

[PubMed - indexed for MEDLINE]
Free PMC Article

Publication Types, MeSH Terms, Substances, Secondary Source ID, Grant Support

PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk