Thiocyanate as a probe of the cystic fibrosis transmembrane conductance regulator chloride channel pore.
Immediately following exposure to thiocyanate (SCN-)-containing solutions, the cystic fibrosis conductance regulator Cl- channel exhibits high unitary SCN conductance and anomalous mole fraction behaviour, suggesting the presence of multiple anion binding sites within the channel pore. However, under steady-state conditions SCN-conductance is very low. Here I show, using patch clamp recording from CFTR-transfected mammalian cell lines, that under steady-state conditions neither SCN- conductance nor SCN- permeability show anomalous mole fraction behaviour. Instead, SCN conductance, permeability, and block of Cl- permeation can all be reproduced by a rate theory model that assumes only a single intrapore anion binding site. These results suggest that under steady-state conditions the interaction between SCN- and the CFTR channel pore can be understood by a simple model whereby SCN- ions enter the pore more easily than Cl-, and bind within the pore more tightly than Cl-. The implications of these findings for investigating and understanding the mechanism of anion permeation are discussed.
Linsdell
P
P
Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada. paul.linsdell@dal.ca
D000818:Animals; D016466:CHO Cells; D002463:Cell Membrane Permeability / Q000502:physiology; D006224:Cricetinae; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D013861:Thiocyanates / Q000378:metabolism*
C505032:CFTR protein, human; D013861:Thiocyanates; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C031760:thiocyanate