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The NH2 terminus of RCK1 domain regulates Ca2+-dependent BK(Ca) channel gating

Gayathri Krishnamoorthy1, Jingyi Shi, David Sept

  • 1Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.

The Journal of General Physiology
|August 17, 2005
PubMed

Insights

The NH2 terminus of RCK1 (AC region) in large conductance, voltage- and Ca2+-activated K+ (BK(Ca)) channels modulates gating. This AC region is crucial for allosteric coupling between Ca2+ binding and channel opening.

Area of Science:

  • Molecular biology
  • Ion channel biophysics
  • Biochemistry

Background:

  • Large conductance, voltage- and Ca2+-activated K+ (BK(Ca)) channels are critical for regulating physiological processes like blood vessel tone, synaptic transmission, and hearing.
  • These channels are activated by both membrane depolarization and intracellular calcium (Ca2+).
  • The structure of similar channels, like MthK, suggests a gating ring formed by RCK domains that reorient upon Ca2+ binding to open the activation gate.

Purpose of the Study:

  • To investigate the role of the NH2 terminus of RCK1 (AC region) in the gating mechanism of BK(Ca) channels.
  • To elucidate how conformational changes in the AC region contribute to the allosteric coupling between Ca2+ binding and channel activation.

Main Methods:

  • The study likely involved electrophysiological techniques to measure channel activity.
  • Mutagenesis studies may have been used to alter the AC region.
  • Biochemical assays could have been employed to assess Ca2+ binding and conformational changes.

Main Results:

  • Conformational changes in the AC region of BK(Ca) channels were found to modulate channel gating.
  • This modulation is dependent on Ca2+ occupancy and the channel's activation state.
  • The AC region's influence on gating is not directly linked to the Ca2+ binding sites themselves.

Conclusions:

  • The AC region plays a significant role in the allosteric coupling between Ca2+ binding and the opening of BK(Ca) channels.
  • Conformational changes within the AC region are an important step in the activation process, in addition to RCK domain reorientation.
  • The AC region appears to inhibit channel activation in the closed state without Ca2+, with this inhibition being relieved by Ca2+ binding and depolarization.

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