Functional expression of a rat homologue of the voltage gated either á go-go potassium channel reveals differences in selectivity and activation kinetics between the Drosophila channel and its mammalian counterpart
Ludwig, J.; Terlau, H.; Wunder, F.; Brüggemann, A.; Pardo, L.A.; Marquardt, A.; Stühmer, W.; Pongs, O.
EMBO Journal 13(19): 4451-4458
1994
ISSN/ISBN: 0261-4189 PMID: 7925287 Document Number: 437582
We have cloned a mammalian (rat) homologue of Drosophila ether a go-go (eag) cDNA, which encodes a distinct type of voltage activated potassium (K) channel. The derived Drosophila and rat eag polypeptides share gt 670 amino acids, with a sequence identity of 61%, exhibiting a high degree of similarity at the N-terminus, the hydrophobic core including the pore forming P region and a potential cyclic nucleotide binding site. Rat eag mRNA is specifically expressed in the central nervous system. In the Xenopus oocyte expression system rat eag mRNA gives rise to voltage activated K channels which have distinct properties in comparison with Drosophila eag channels and other voltage activated K channels. Thus, the rat eag channel further extends the known diversity of K channels. Most notably, the kinetics of rat eag channel activation depend strongly on holding membrane potential. Hyperpolarization slows down the kinetics of activation; conversely depolarization accelerates the kinetics of activation. This novel K channel property may have important implications in neural signal transduction allowing neurons to tune their repolarizing properties in response to membrane hyperpolarization.