Internal blockade of a Ca(2+)-activated K+ channel by Shaker B inactivating "ball" peptide.
Shaker B inactivating peptide ("ball peptide", BP) interacts with Ca(2+)-activated K+ (KCa) channels from the cytoplasmic side only, producing inhibition of channel activity. This effect was reversible and dose and voltage dependent (stronger at depolarized potentials). The inhibition of KCa channels by BP cannot be mimicked by an inactive point mutation of the BP, L7E. BP binds to KCa channels in a bimolecular reaction (dissociation constant of 95 microM at +40 mV). The binding site is probably located in the internal "mouth" or conduction pathway, since both external K+ and internal tetraethylammonium relieve BP-induced inhibition. These results suggest that KCa channels possess a binding site for the BP with some properties similar to the ball receptor found in Shaker B K+ channels.
Toro
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L
Department Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030.
Stefani
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E
Latorre
R
R
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology*; D004594:Electrophysiology; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000494:pharmacology*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D013552:Swine; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D047908:Intracellular Signaling Peptides and Proteins; D010446:Peptide Fragments; D010455:Peptides; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; C076103:Shaker B inactivating peptide; D019789:Tetraethylammonium; D011188:Potassium; D002118:Calcium