TY - JOUR
AU1 - Perez-Cornejo, P.
AU2 - Santiago, J.
AU3 - Arreola, J.
AB - The effects of external anions (SCN−, NO
3
−
, I−, Br−, F−, glutamate, and aspartate) on gating of Ca2+-dependent Cl− channels from rat parotid acinar cells were studied using the whole-cell configuration of the patch-clamp technique. Shifts in the reversal potential of the current induced by replacement of external Cl− with foreign anions, gave the following selectivity sequence based on permeability ratios (P
x/P
Cl): SCN−>I−>NO
3
−
>Br−>Cl−>F−>aspartate>glutamate. Using a continuum electrostatic model we calculated that this lyotropic sequence resulted from the interaction between anions and a polarizable tunnel with an effective dielectric constant of ∼23. Our data revealed that anions with P
x/PCl > 1 accelerated activation kinetics in a voltage-independent manner and slowed deactivation kinetics. Moreover, permeant anions enhanced whole-cell conductance (g, an index of the apparent open probability) in a voltage-dependent manner, and shifted leftward the membrane potential-g curves. All of these effects were produced by the anions with an effectiveness that followed the selectivity sequence. To explain the effects of permeant anions on activation kinetics and g
Cl we propose that there are 2 different anion-binding sites in the channel. One site is located outside the electrical field and controls channel activation kinetics, while a second site is located within the pore and controls whole-cell conductance. Thus, interactions of permeant anions with these two sites hinder the closing mechanism and stabilize the channel in the open state.
TI - Permeant Anions Control Gating of Calcium-dependent Chloride Channels
JF - The Journal of Membrane Biology
DO - 10.1007/s00232-004-0659-x
DA - 2004-01-01
UR - https://www.deepdyve.com/lp/springer-journals/permeant-anions-control-gating-of-calcium-dependent-chloride-channels-MOJZwK0270
SP - 125
EP - 133
VL - 198
IS - 3
DP - DeepDyve
ER -