Molecular determinants of external barium block in Shaker potassium channels.
Mutations in the outer pore region of Shaker K+ channels (T449 and D447) can influence external Ba2+ block. Substitution of T449 by A, V or Y differentially reduced Ba2+ block primarily by decreasing the blocking rate. Substitution of D447 by N resulted in a non-conducting channel with apparently normal gating currents. External Ba2+ can speed the OFF gating current of a different non-conducting mutant, W434F; this effect was markedly attenuated by the D447N substitution. These results suggest that D447 contributes to an external Ba2+ binding site while T449 imposes a barrier to the access of that site.
Hurst
R S
RS
Department of Anesthesiology, University of California at Los Angeles, CA 90095, USA.
Toro
L
L
Stefani
E
E
D000818:Animals; D001224:Aspartic Acid / Q000502:physiology*; D001464:Barium / Q000494:pharmacology*; D001665:Binding Sites; D002413:Cations, Divalent; D015640:Ion Channel Gating / Q000187:drug effects*; D009154:Mutation; D009865:Oocytes; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D051637:Shaker Superfamily of Potassium Channels; D013912:Threonine / Q000502:physiology*; D014982:Xenopus laevis
D002413:Cations, Divalent; D015221:Potassium Channels; D051637:Shaker Superfamily of Potassium Channels; D001464:Barium; D013912:Threonine; D001224:Aspartic Acid