Large conductance Ca2+-activated K+ (BK) channel: Activation by Ca2+ and voltage
Biol. Res
; 39(3): 385-401, 2006. ilus
Artigo
em Inglês
| LILACS
| ID: lil-437374
Biblioteca responsável:
BR1.1
ABSTRACT
Large conductance Ca2+-activated K+ (BK) channels belong to the S4 superfamily of K+ channels that include voltage-dependent K+ (Kv) channels characterized by having six (S1-S6) transmembrane domains and a positively charged S4 domain. As Kv channels, BK channels contain a S4 domain, but they have an extra (S0) transmembrane domain that leads to an external NH2-terminus. The BK channel is activated by internal Ca2+, and using chimeric channels and mutagenesis, three distinct Ca2+-dependent regulatory mechanisms with different divalent cation selectivity have been identified in its large COOH-terminus. Two of these putative Ca2+-binding domains activate the BK channel when cytoplasmic Ca2+ reaches micromolar concentrations, and a low Ca2+ affinity mechanism may be involved in the physiological regulation by Mg2+. The presence in the BK channel of multiple Ca2+-binding sites explains the huge Ca2+ concentration range (0.1 ìM-100 ìM) in which the divalent cation influences channel gating. BK channels are also voltage-dependent, and all the experimental evidence points toward the S4 domain as the domain in charge of sensing the voltage. Calcium can open BK channels when all the voltage sensors are in their resting configuration, and voltage is able to activate channels in the complete absence of Ca2+. Therefore, Ca2+ and voltage act independently to enhance channel opening, and this behavior can be explained using a two-tiered allosteric gating mechanism.
Texto completo:
Disponível
Coleções:
Bases de dados internacionais
Base de dados:
LILACS
Assunto principal:
Canais de Cálcio
/
Canais de Potássio Ativados por Cálcio de Condutância Alta
Limite:
Animais
Idioma:
Inglês
Revista:
Biol. Res
Assunto da revista:
Biologia
Ano de publicação:
2006
Tipo de documento:
Artigo
/
Documento de projeto
País de afiliação:
Chile
Instituição/País de afiliação:
Centro de Estudios Científicos/CL