Functional characterization of K-v channel beta-subunits from rat brain

1. The potassium channel beta-subunit from rat brain, K-V beta 1.1, is known to induce inactivation of the delayed rectifier channel K(V)1.1 and K(V)1.4 Delta 1-110. 2. K-V beta 1.1 was co-expressed in Xenopus oocytes with various other potassium channel alpha-subunits. K-V beta 1.1 induced inactivation in members of the K(V)1 subfamily with the exception of K(V)1.6; no inactivation of K(V)2.1, K(V)3.4 Delta 2-28 and K(V)4.1 channels could be observed. 3. The second member of the beta-subunit subfamily K-V beta 2, had a shorter N-terminal end, accelerated inactivation of the A-type channel K(V)1.4, but did not induce inactivation when co-expressed with delayed rectifiers of the K(V)1 channel family. 4. To test whether this subunit co-assembles with K-V alpha-subunits, the N-terminal inactivating domains of K-V beta 1.1 and K-V beta 3 were spliced to the N-terminus of K-V beta 2. The chimaeric beta-subunits (beta 1/beta 2 and beta 3/beta 2) induced fast inactivation of several K(V)1 channels, indicating that K-V beta 2 associates with these alpha-subunits. No inactivation was induced in K(V)1.3, K(V)1.6, K(V)2.1 and K(V)3.4 Delta 2-28 channels. 5. K-V beta 2 caused a voltage shift in the activation threshold of K(V)1.5 of about -10 mV, indicating a putative physiological role. K-V beta 2 had a smaller effect on K(V)1.1 channels. 6. K-V beta 2 accelerated the activation time course of K(V)1.5 but had no marked effect on channel deactivation.