Stability of the Shab K+ channel conductance in 0 K+ solutions: the role of the membrane potential.
Biophys J
; 93(12): 4197-208, 2007 Dec 15.
Article
em En
| MEDLINE
| ID: mdl-17704149
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.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Potássio
/
Ativação do Canal Iônico
/
Spodoptera
/
Canais de Potássio Shab
/
Potenciais da Membrana
Limite:
Animals
Idioma:
En
Revista:
Biophys J
Ano de publicação:
2007
Tipo de documento:
Article
País de afiliação:
México
País de publicação:
Estados Unidos