| Potassium channels are found in many cells and play a role in modulating membrane excitability. One family consists of two-pore domain K+ channels (TPCs). A distinct TPC from Drosophila melanogaster has been isolated, characterized, and designated TPC1. RACE and sequence analyses of TPC1 suggest it is variable with respect to alternative splicing and/or promoter utilization. TPC1 arises from two distinct transcriptional start sites located 628 by apart, which share a common initiator methionine. TPC1 also exhibits alternative splicing at the 3′ end. The current study identified three distinct variants corresponding to the intracellular carboxyl-terminal. Two of the deletion variants result in truncated proteins whereas the TPC1 protein predicted from fully-sequenced cDNAs, corresponds to a full-length variant consisting of 918 amino acids. Splicing at the carboxyl-terminal results from the utilization of both conventional and non-conventional splice sites. Northern blot analysis was also performed to determine temporal variation. Sequence analysis suggested that TPC1 is most homologous with human TREK-1, a mammalian two-pore domain potassium channel. |
