Submitted on August 16, 2005
Accepted on January 27, 2006
Atypical Phenotypes from Flatworm Kv3 channels
Tara L. Klassen1, Steven D. Buckingham2, Donna M. Atherton1, Joel B. Dacks3, Warren J. Gallin4, and Andrew N. Spencer4*
1 Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
2 Human Anatomy and Genetics, University of Oxford, Oxford, United Kingdom; Bamfield Marine Sciences Centre, Bamfield, BC, Canada
3 Biological Sciences, University of Calgary, Calgary, Alberta, Canada
4 Biological Sciences, University of Alberta, Edmonton, Alberta, Canada; Bamfield Marine Sciences Centre, Bamfield, BC, Canada
* To whom correspondence should be addressed. E-mail: andy.spencer{at}shaw.ca.
Tara Klassen, Steven Buckingham, Donna Atherton, Joel Dacks, Warren Gallin, Andrew Spencer. 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 emphasises 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 non-inactivating, 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.
