K channels of the Shaker family

The molecular analysis of the Sh K channel transcription unit indicated that at least ten different channel subunits may be expressed in Drosophila cells. This observation raised a number of important questions only some of them can be addressed here. Each subunit has been expressed in the Xenopus oocyte expression system [11,12,29,39]. These experiments indicate that each subunit expresses distinct 

Time constants and mean single-channel open times of Shaker K. channel splice variants 

Inactivation time constants are from [39,62], mean single channel open times are from [29,43]. Values were obtained at 0 mV test potentials. In the case of S/iAl, Sh 2 and 5AB2 s 5-15% of peak current inactivates slowly, i.e., with the time constant l2- n.d. = not determined. 

Properties of Shaker channels in Drosophila muscle and photoreceptor cells  

Cell type Kt/2 (mV) f /2 (mV) Single-channel open times (ms) Single-channel slope conductance (pS) 

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