Slob, a novel protein that binds to the carboxy-terminal domain of the Drosophila Slowpoke (dSIo) calcium-dependent potassium channel, was identified with a yeast two-hybrid screen. Slob and dSIo coimmunoprecipitate from Drosophila heads and heterologous host cells, suggesting that they interact in vivo. Slob also coimmunoprecipitates with the Drosophila FAG potassium channel but not with Drosophila Shaker, mouse Slowpoke, or rat K(v)l.3. Confocal fluorescence microscopy demonstrates that Slob and dSIo redistribute in cotransfected cells and are colocalized in large intracellular structures. Direct application of Slob to the cytoplasmic face of detached membrane patches containing dSIo channels leads to an increase in channel activity. Slob may represent a new class of multi-functional channel- binding proteins.
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