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Cloned auxiliary {beta}-subunits (e.g.Kv{beta}1) modulate the kinetic properties of the pore-forming -subunits of a subset of Shaker-like potassium channels. Coexpression of the -subunit and Kv{beta}2, however, induces little change in channel properties. Since more than one {beta}-subunit has been found in individual K+ channel complexes and expression patterns of different {beta}-subunits overlap in vivo, it is important to test the possible physical and/or functional interaction(s) between different {beta}-subunits. In this report, we show that both Kv{beta}2 and Kv{beta}1 recognize the same region on the pore-forming -subunits of the Kv1 Shaker-like potassium channels. In the absence of -subunits the Kv{beta}2 polypeptide interacts with additional {beta}-subunit(s) to form either a homomultimer with Kv{beta}2 or a heteromultimer with Kv{beta}1. When coexpressing -subunits and Kv{beta}1 in the presence of Kv{beta}2, we find that Kv{beta}2 is capable of inhibiting the Kv{beta}1-mediated inactivation. Using deletion analysis, we have localized the minimal interaction region that is sufficient for Kv{beta}2 to associate with both -subunits and Kv{beta}1. This mapped minimal interaction region is necessary and sufficient for inhibiting the Kv{beta}1-mediated inactivation, consistent with the notion that the inhibitory activity of Kv{beta}2 results from the coassembly of Kv{beta}2 with compatible -subunits and possibly with Kv{beta}1. Together, these results provide biochemical evidence that Kv{beta}2 may profoundly alter the inactivation activity of another {beta}-subunit by either differential subunit assembly or by competing for binding sites on -subunits, which indicates that Kv{beta}2 is capable of serving as an important determinant in regulating the kinetic properties of K+currents.
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