A human intermediate conductance calcium-activated potassium channel

• DOI: 10.1073/pnas.94.21.11651
• Publication Date: 2002-07-26T14:31:44Z
• Authors: Takahiro M. Ishii; Christopher Silvia; Birgit Hirschberg; Chris T. Bond; John P. Adelman; James Maylie
• Keywords: Calcium-activated potassium channel; Apamin; BK channel; Iberiotoxin; SK channel; N-type calcium channel; Potassium channel blocker; Calcium in biology

An intermediate conductance calcium-activated potassium channel, hIK1, was cloned from human pancreas. The predicted amino acid sequence is related to, but distinct from, the small channel subfamily, which ≈50% conserved. hIK1 mRNA detected in peripheral tissues not brain. Expression of Xenopus oocytes gave rise to inwardly rectifying currents, were activated by submicromolar concentrations intracellular calcium ( K 0.5 = 0.3 μM). Although for similar that channels, slope factor derived Hill equation significantly reduced (1.7 vs. 3.5). Single-channel current amplitudes reflected macroscopic inward rectification and revealed a level 39 pS direction. currents reversibly blocked charybdotoxin (K i 2.5 nM) clotrimazole 24.8 minimally affected apamin (100 nM), iberiotoxin (50 or ketoconazole (10 These biophysical pharmacological properties are consistent with native including erythrocyte Gardos channel.