Subunit combinations defined for K+ channel Kv1 subtypes in synaptic membranes from bovine brain

Voltage-dependent Shaker-related (Kv1) K+ channels are composed of transmembrane a subunits and peripheral Kv beta proteins that exist as octomers with (alpha)(4)(beta)(4) stoichiometry. Although several a (designated Kv1.X) and three Kv beta subunits are known to be expressed in brain, their oligomeric combinations in neurons have yet to be deciphered. Herein, the subunits comprising a number of neuronal K+ channels from bovine brain cortex were deduced by immunoprecipitation and Western blotting, using antibodies specific for Kv1.X and Kv beta subtypes. Only a subset of the theoretically possible oligomers was detected, showing that the synthesis and/or assembly of these multisubunit K+ proteins is controlled to yield a limited variety of K+ channels. Except for a small population of Kv1.4 containing K+ channels, all the recognizable species contained Kv1.2 and beta 2 subunits. Furthermore, several subpopulations were identified including a fully defined complex of Kv1.2/1.3/1.4/1.6 and Kv beta 2, plus oligomers containing three or two assigned a subunits. Kv1.2 was also shown to occur in the absence of these other subunits as a putative homo-oligomer. Thus, for the first time, the complete subunit combination of an authentic K+ channel has been elucidated; also, the strategy employed to establish this can now be applied to closely related members of other K+ channel families.