AJP - Cell Physiology, Vol 262, Issue 4 C971-C974, Copyright © 1992 by American Physiological Society
Effect of trypsin on a Ca(2+)-activated K+ channel reconstituted into planar phospholipid bilayers
L. Salomao, G. Wark, W. P. Dubinsky and S. G. Schultz
Department of Physiology and Cell Biology, University of Texas Medical School, Houston 77030.
Exposure of the cytoplasmic side of calcium-activated, high
(maxi)-conductance potassium [BK(Ca)] channels in basolateral membrane
vesicles from rabbit colonocytes incorporated into planar phospholipid
bilayers to trypsin rapidly reduces, but does not abolish, the sensitivity
of this channel to activation by calcium without affecting its conductance
or high selectivity for K+ over Cl-. The results of these studies also
indicate that this BK(Ca) channel does not have intrinsic voltage-gating
properties but that its voltage sensitivity is related to its ability to
interact with calcium. This conclusion is consistent with the model
proposed by Moczydlowski and Lattore (J. Gen. Physiol. 82: 511-542, 1983)
for the role of membrane voltage in modulating the interaction between
calcium and the BK(Ca) channel in rat skeletal muscle.
