The beta subunit, Kv beta 1.2, acts as a rapid open channel blocker of NH2-terminal deleted Kv1.4 alpha-subunits

A recently discovered class of ancillary subunits has been shown to modify the inactivation properties of alpha-subunits belonging to the Kv1 family of potassium channels. One of these subunits, Kv beta 1.2, modifies intrinsic alpha-subunit C-type inactivation. N-type inactivation and open channel block have been proposed to increase the rate of development of C-type inactivation. We demonstrate here that Kv beta 1.2 has kinetic properties which are consistent with rapid open channel block.