Gating kinetics of Ca++-activated K+ channels from rat muscle incorporated into planar lipid bilayers: Evidence for two voltage-dependent Ca2+ binding reactions
Author
dc.contributor.author
Moczydlowski, Edward
Author
dc.contributor.author
Latorre, Ramón
Admission date
dc.date.accessioned
2019-01-29T14:20:46Z
Available date
dc.date.available
2019-01-29T14:20:46Z
Publication date
dc.date.issued
1983
Cita de ítem
dc.identifier.citation
Journal of General Physiology, Volume 82 October 1983 511-542
Identifier
dc.identifier.issn
15407748
Identifier
dc.identifier.issn
00221295
Identifier
dc.identifier.other
10.1085/jgp.82.4.511
Identifier
dc.identifier.uri
https://repositorio.uchile.cl/handle/2250/160503
Abstract
dc.description.abstract
The gating kinetics of a Ca2+-activated K+ channel from adult rat muscle plasma membrane are studied in artificial planar bilayers. Analysis of single-channel fluctuations distinguishes two Ca2+- and voltage-dependent processes: (a) short-lived channel closure (<1 ms) events appearing in a bursting pattern; (b) opening and closing events ranging from one to several hundred milliseconds in duration. The latter process is studied independently of the first and is denoted as the primary gating mode. At constant voltage, the mean open time of the primary gating mode is a linear function of the [Ca2+, whereas the mean closed time is a linear function of the reciprocal [Ca2+]. In the limits of zero and infinite [Ca2+], the mean open and the mean closed times are, respectively, independent of voltage. These results are predicted by a kinetic scheme consisting of the following reaction steps: (a) binding of Ca2+ to a closed state; (b) channel opening; (c) binding of a second Ca2+ ion. In this scheme, the
two Ca2+ binding reactions are voltage dependent, whereas the open-closed
transition is voltage independent. The kinetic constant derived for this scheme
gives an accurate theoretical fit to the observed equilibrium open-state probability . The results provide evidence for a novel regulatory mechanism for the
activity of an ion channel : modulation by voltage of the binding of an agonist
molecule, in this case, Ca2+ ion .
Gating kinetics of Ca++-activated K+ channels from rat muscle incorporated into planar lipid bilayers: Evidence for two voltage-dependent Ca2+ binding reactions