Locked-Open Activation Gate Prevents the Recovery of Shaker K+ Channels from Slow Inactivation

摘要: In the absence of N-type inactivation Shaker potassium channels display slow (C-type) inactivation. It has been shown earlier that Cd2+ traps V476C in open state, even at very negative voltages, by forming a metal bridge between cysteine one subunit and native histidine (H486) neighboring (Webster et al., Nature, 2004). However, none previous studies determined relationship inactivation/recovery from locked-open activation gate. The current experiments tested hypothesis locking gate configuration prevents recovery To address this we compared extent for control conditions presence 20 µM Cd2+. V476C/IR contained an alanine position 449 to facilitate entry into slow-inactivated state. All ionic were performed with excised inside-out patches. A fast-step perfusion system was used rapid solution exchange. 2.0-s-long depolarizing pulses holding potential −120 mV +50 applied when applicable, added fully inactivated channels. duration pulse 1.0 s long which started 800 ms after start depolarization. Under 100% recovered within 60 mV, whereas upon application less than 10 % under identical (n=3). lack suggests closure is essential