Fast single-channel measurements resolve the blocking effect of Cs+ on the K+ channel.
AUTOR(ES)
Draber, S
RESUMO
The Cs+ block of K+ channels has often been investigated by methods that allow only indirect estimation of the rate constants of blocking and re-opening. This paper presents single-channel records with high temporal resolution which make the direct observation of the fast transitions between the blocked and the unblocked state possible. The rate constants kOGb, kGbO of Cs(+)-dependent blocking and of re-opening are evaluated from the time constants found in the open-time and closed-time histograms. The blocking rate constant kOGb between 1000 and 50000 s-1 depends linearly on the Cs+ concentration and strongly on voltage, increasing by a factor of 1.44 per 10 mV hyperpolarization. The re-opening rate constant kGbO approximately 30000 s-1 is independent of Cs+ concentration and only slightly voltage-dependent. Formally, the results can be described by a Woodhull-model. The strong voltage dependence with d > 1, however, weakens its plausibility. The results are interpreted in terms of a molecular framework emerging from recent results on the structure of voltage-gated channels.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1225341Documentos Relacionados
- Single-channel events and gating behavior of the cardiac gap junction channel.
- Single-channel properties of a rat brain endoplasmic reticulum anion channel.
- A helical-dipole model describes the single-channel current rectification of an uncharged peptide ion channel.
- Single-channel analysis of fast transient potassium currents from rat nodose neurones.
- Ca2(+)-activated K+ current involvement in neuronal function revealed by in situ single-channel analysis in Helix neurones.