Biophys J, August 2001, p. 814-826, Vol. 81, No. 2

U-Type Inactivation of Kv3.1 and Shaker Potassium Channels

Kathryn G. Klemic,^* Glenn E. Kirsch,^* and Stephen W. Jones^*

 ^*Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106 and  Rammelkamp Center for Research, MetroHealth Medical Center, Cleveland, Ohio 44109 USA

We previously concluded that the Kv2.1 K⁺ channel inactivates preferentially from partially activated closed states. We report here that the Kv3.1 channel also exhibits two key features of this inactivation mechanism: a U-shaped voltage dependence measured at 10 s and stronger inactivation with repetitive pulses than with a single long depolarization. More surprisingly, slow inactivation of the Kv1 Shaker K⁺ channel (Shaker B6-46) also has a U-shaped voltage dependence for 10-s depolarizations. The time and voltage dependence of recovery from inactivation reveals two distinct components for Shaker. Strong depolarizations favor inactivation that is reduced by K or by partial block by TEA_o, as previously reported for slow inactivation of Shaker. However, depolarizations near 0 mV favor inactivation that recovers rapidly, with strong voltage dependence (as for Kv2.1 and 3.1). The fraction of channels that recover rapidly is increased in TEA_o or high K. We introduce the term U-type inactivation for the mechanism that is dominant in Kv2.1 and Kv3.1. U-type inactivation also makes a major but previously unrecognized contribution to slow inactivation of Shaker.

Biophys J, August 2001, p. 814-826, Vol. 81, No. 2
© 2001 by the Biophysical Society   0006-3495/01/08/814/13  $2.00

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