Kcnkø: single, cloned potassium leak channels are multi-ion pores.
KCNKØ was the first clone to show attributes of a leak conductance: voltage-independent potassium currents that develop without delay. Its novel product is predicted to have two nonidentical P domains and four transmembrane segments and to assemble in pairs. Here, the mechanistic basis for leak is examined at the single-channel level. KCNKØ channels open at all voltages in bursts that last for minutes with open probability close to 1. The channels also enter a minutes-long closed state in a tightly regulated fashion. KCNKØ has a common relative permeability series (Eisenman type IV) but conducts only thallium and potassium readily. KCNKØ exhibits concentration-dependent unitary conductance, anomalous mole fraction behavior, and pore occlusion by barium. These observations argue for ion-channel and ion-ion interactions in a multi-ion pore and deny the operation of independence or constant-field current formulations. Despite their unique function and structure, leakage channels are observed to operate like classical potassium channels formed with one-P-domain subunits.
Ilan
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Department of Pediatrics, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06536, USA.
Goldstein
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SA
D000818:Animals; D001464:Barium / Q000494:pharmacology; D055592:Biophysical Phenomena; D001703:Biophysics; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics / Q000378:metabolism; D004563:Electrochemistry; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials; D009865:Oocytes / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis
D029721:Drosophila Proteins; C102352:Ork1 protein, Drosophila; D015221:Potassium Channels; D011994:Recombinant Proteins; D001464:Barium