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.
We have cloned a mammalian (rat) homologue of Drosophila ether á go-go (eag) cDNA, which encodes a distinct type of voltage activated potassium (K) channel. The derived Drosophila and rat eag polypeptides share > 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.
Ludwig
J
J
ZMNH, Institut für neurale Signalverarbeitung, Hamburg, Germany.
Terlau
H
H
Wunder
F
F
Brüggemann
A
A
Pardo
L A
LA
Marquardt
A
A
Stühmer
W
W
Pongs
O
O
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary; D004330:Drosophila; D029721:Drosophila Proteins; D051638:Ether-A-Go-Go Potassium Channels; D015640:Ion Channel Gating / Q000502:physiology; D008297:Male; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000502:physiology; D009865:Oocytes / Q000378:metabolism; D016133:Polymerase Chain Reaction; D015221:Potassium Channels / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000096:biosynthesis; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014982:Xenopus laevis
D018076:DNA, Complementary; D029721:Drosophila Proteins; D051638:Ether-A-Go-Go Potassium Channels; C496886:Kcnh1 protein, rat; D009419:Nerve Tissue Proteins; D015221:Potassium Channels; D012333:RNA, Messenger; D011994:Recombinant Proteins; C496883:eag protein, Drosophila