Identification of a novel tetramerization domain in large conductance K-Cachannels

More than 50 genes are known to encode K+ channel monomers and can coassemb le to form hetero-tetrameric K+ channels. However, only a subset of possibl e monomer combinations come together to form functional ion channels. The a ssembly and tetramerization of appropriate channel monomers is mediated by association domains (ADs). To identify such domains in human large-conducta nce Ca2(+)-activated K+ channels (hSlo1), we screened hSlo1 domains for sel f-association using yeast two-hybrid assays. Putative ADs were subjected to functional assays in Xenopus oocytes and further characterized by co preci pitation, native gel electrophoresis, and sucrose density gradient centrifu gation assays. This led to the identification of a single intracellular ass ociation domain localized near the channel pore and required for channel fu nction. We conclude that this novel tetramerization domain, referred to as BK-T1, promotes the assembly of hSlo1 monomers into functional Kc channels.