K+ transport characteristics of the plasma membrane tandem-pore channel TPK4 and pore chimeras with its vacuolar homologs.
Vacuolar tandem-pore channels could not be analysed in Xenopus oocytes so far, due to misguided translocation. Owing to the conservation of their pore regions, we were able to prepare functional pore-chimeras between the plasma membrane localised TPK4 and vacuolar TPKs. Thereby, we found evidence that TPK2, TPK3 and TPK5, just like TPK4, form potassium-selective channels with instantaneous current kinetics. Homology modelling and mutational analyses identified a pore-located aspartate residue (Asp110), which is involved in potassium permeation as well as in inward rectification of TPK4. Furthermore, dominant-negative mutations in the selectivity filter of either pore one or two (Asp86,Asp200) rendered TPK4 non-functional. This observation supports the notion that the functional TPK4 channel complex is formed by two subunits.
Marcel
Dunkel
D
Department of Molecular Plant Physiology and Biophysics, University of Würzburg, Würzburg, Germany.
Müller
Thomas
T
Hedrich
Rainer
R
Geiger
Dietmar
D
D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D022082:Cellular Structures / Q000378:metabolism; D002678:Chimera / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism
D007473:Ion Channels; D015221:Potassium Channels; D011188:Potassium