Surface Charges of K channels. Effects of strontium on five cloned channels expressed in Xenopus oocytes.
The effects of strontium (Sr2+; 7-50 mM) on five different cloned rat K channels (Kv1.1, Kv1.5, Kv1.6, Kv2.1, and Kv3.4), expressed in oocytes of Xenopus laevis, were investigated with a two-electrode voltage clamp technique. The main effect was a shift of the Gk(V) curve along the potential axis, different in size for the different channels. Kv1.1 was shifted most and Kv3.4 least, 21 and 8 mV, respectively, at 50 mM. The effect was interpreted in terms of screening of fixed surface charges. The estimated charge densities ranged from -0.37 (Kv1.1) to -0.11 (Kv3.4) e nm-2 and showed good correlation with the total net charge of the extracellularly located amino acid residues of the channel as well as with the charge of a specific region (the loop between the S5 segment and the pore forming segment). The estimated surface potentials were found to be linearly related to the activation midpoint potential, suggesting a functional role for the surface charges.
Elinder
F
F
Nobel Institute for Neurophysiology, Karolinska Institutet, Stockholm, Sweden.
Madeja
M
M
Arhem
P
P
D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D004553:Electric Conductivity; D004594:Electrophysiology; D005260:Female; D009865:Oocytes / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D051381:Rats; D013324:Strontium / Q000494:pharmacology*; D014982:Xenopus laevis
D015221:Potassium Channels; D013324:Strontium