This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.106.095794v1 93/12/4197    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Gómez-Lagunas, F. Search for Related Content PubMed PubMed Citation Articles by Gómez-Lagunas, F.

Stability of the Shab K⁺ Channel Conductance in 0 K⁺ Solutions: The Role of the Membrane Potential

Facultad de Medicina, Dept. Fisiologia, Universidad Nacional Autónoma de México, Ciudad Universitaria, Apartado Postal 70-250 Mexico D.F. 04510, Mexico

Correspondence: Address reprint requests to Froylán Gómez-Lagunas, Facultad de Medicina, Dept. Fisiologia, Universidad Nacional Autónoma de México, Ciudad Universitaria, Apartado Postal 70-250 Mexico D.F. 04510, Mexico. Tel.: 555-623-2263; E-mail: froylangl{at}yahoo.com.

Shab channels are fairly stable with K⁺ present on only one side of the membrane. However, on exposure to 0 K⁺ solutions on both sides of the membrane, the Shab K⁺ conductance (G_K) irreversibly drops while the channels are maintained undisturbed at the holding potential. Herein it is reported that the drop of G_K follows first-order kinetics, with a voltage-dependent decay rate r. Hyperpolarized potentials drastically inhibit the drop of G_K. The G_K drop at negative potentials cannot be explained by a shift in the voltage dependence of activation. At depolarized potentials, where the channels undergo a slow inactivation process, G_K drops in 0 K⁺ with rates slower than those predicted based on the behavior of r at negative potentials, endowing the r-V_m relationship with a maximum. Regardless of voltage, r is very small compared with the rate of ion permeation. Observations support the hypothesized presence of a stabilizing K⁺ site (or sites) located either within the pore itself or in its external vestibule, at an inactivation-sensitive location. It is argued that part of the G_K stabilization achieved at hyperpolarized potentials could be the result of a conformational change in the pore itself.