Atypical phenotypes from flatworm Kv3 channels.
Divergence of the Shaker superfamily of voltage-gated (Kv) ion channels early in metazoan evolution created numerous electrical phenotypes that were presumably selected to produce a wide range of excitability characteristics in neurons, myocytes, and other cells. A comparative approach that emphasizes this early radiation provides a comprehensive sampling of sequence space that is necessary to develop generally applicable models of the structure-function relationship in the Kv potassium channel family. We have cloned and characterized two Shaw-type potassium channels from a flatworm (Notoplana atomata) that is arguably a representative of early diverging bilaterians. When expressed in Xenopus oocytes, one of these cloned channels, N.at-Kv3.1, exhibits a noninactivating, outward current with slow opening kinetics that are dependent on both the holding potential and the activating potential. A second Shaw-type channel, N.at-Kv3.2, has very different properties, showing weak inward rectification. These results demonstrate that broad phylogenetic sampling of proteins of a single family will reveal unexpected properties that lead to new interpretations of structure-function relationships.
Klassen
Tara L
TL
Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E1.
Buckingham
Steven D
SD
Atherton
Donna M
DM
Dacks
Joel B
JB
Gallin
Warren J
WJ
Spencer
Andrew N
AN
D000818:Animals; D003001:Cloning, Molecular / Q000379:methods; D004307:Dose-Response Relationship, Radiation; D004553:Electric Conductivity; D004558:Electric Stimulation / Q000379:methods; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D008845:Microinjections / Q000379:methods; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D010641:Phenotype; D010802:Phylogeny; D010986:Platyhelminths / Q000235:genetics*; D011188:Potassium / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D017422:Sequence Analysis, DNA / Q000379:methods; D020539:Sequence Analysis, Protein / Q000379:methods; D051670:Shaw Potassium Channels / Q000235:genetics* / Q000502:physiology
D012333:RNA, Messenger; D051670:Shaw Potassium Channels; D011188:Potassium