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The Journal of Neuroscience, March 1, 2002, 22(5):1550-1561

Consequences of the Stoichiometry of Slo1  and Auxiliary  Subunits on Functional Properties of Large-Conductance Ca²⁺-Activated K⁺ Channels

Ying-Wei Wang, Jiu Ping Ding, Xiao-Ming Xia, and Christopher J. Lingle

Departments of Anesthesiology and Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110

Auxiliary  subunits play a major role in defining the functional properties of large-conductance, Ca²⁺-dependent BK-type K⁺ channels. In particular, both the 1 and 2 subunits produce strong shifts in the voltage dependence of channel activation at a given Ca²⁺.  subunits are thought to coassemble with  subunits in a 1:1 stoichiometry, such that a full ion channel complex may contain up to four  subunits per channel. However, previous results raise the possibility that ion channels with less than a full complement of  subunits may also occur. The functional consequence of channels with differing stoichiometries remains unknown. Here, using expression of  and  subunits in Xenopus oocytes, we show explicitly that functional BK channels can arise with less than four  subunits. Furthermore, the results show that, for both the 1 and 2 subunits, each individual  subunit produces an essentially identical, incremental effect on the voltage dependence of gating. For channels arising from  + 2 subunits, the number of 2 subunits per channel also has a substantial impact on properties of steady-state inactivation and recovery from inactivation. Thus, the stoichiometry of : subunit assembly can play a major functional role in defining the apparent Ca²⁺ dependence of activation of BK channels and in influencing the availability of BK channels for activation.

Key words: auxiliary subunits; BK channels; Ca²⁺- and voltage-gated K⁺ channels; Slo1 channels; inactivation; ion channel stoichiometry; gating mechanisms

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Copyright © 2002 Society for Neuroscience  0270-6474/02/2251550-12$05.00/0

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