Jennifer Yao

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4-Aminopyridine (4AP) can block various K channels with different state dependences; block occurs in the activated state or in the closed state. The use of K channel clones to study the mechanism and structural determinants responsible for the state dependence of 4AP actions has been hampered by the fact that, for all the K channel clones examined so far,(More)
It has been shown for a Shaker channel (H-4) that its NH2-terminal cytoplasmic domain may form a "ball and chain" structure, with the "chain" tethering the "ball" to the channel while the "ball" capable of binding to the channel in its open state and causing inactivation. Equivalent structures have not been identified in mammalian Shaker homologues. We(More)
We studied the effects of quinidine on two K channel clones expressed in Xenopus oocytes, Kv1.2 and Kv1.4. Quinidine had an agonist (enhancement) and a blocker (suppression) action on Kv1.2, whereas only the blocker action was seen with Kv1.4. For both, the blocker action was exerted from the intracellular side of the membrane due to quinidine binding in(More)
We examined the state-, voltage-, and time dependences of interaction between 4-AP and a mammalian A-type K channel clone (rKv1.4) expressed in Xenopus oocytes using whole-cell and single-channel recordings. 4-AP blocked rKv1.4 from the cytoplasmic side of the membrane. The development of block required channel opening. Block was potentiated by removing the(More)
To explore the role of sulfhydryl (SH) groups in the function of cardiac slow delayed rectifier channels, we tested the effects of extracellular thimerosal (TMS, a hydrophilic SH modifier) on slow delayed rectifier current (IKs) induced by human IsK (hIsK) in oocytes and on the native IKs in canine ventricular myocytes. TMS (25 or 50 microM) had similar(More)
n-Dodecylguanidine (C12-G) is an amphipathic compound with a guanidine moiety, which is positively charged at physiological pH, and a hydrophobic side chain. Its effects on an A-type K+ channel clone (rKv1.4) expressed in Xenopus oocytes were examined. C12-G caused a concentration-dependent (1-20 microM) positive shift in the voltage dependences of the(More)
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