Role of surface electrostatics in the operation of a high-conductance Ca2+-activated K+ channel |
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Authors: | R MacKinnon R Latorre C Miller |
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Institution: | Howard Hughes Medical Institute, Brandeis University, Waltham, Massachusetts 02254. |
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Abstract: | This paper demonstrates that local electric fields originating from negatively charged groups on a K+-specific ion channel modify its behavior. Single high-conductance, Ca2+-activated K+ channels were studied in neutral phospholipid bilayers. The channel protein surface charges were manipulated experimentally by carboxyl group esterification using trimethyloxonium (TMO) or by electrolyte screening. Three channel properties--ion conduction, ion blockade, and voltage-dependent gating--are affected by surface electrostatics. Negative charges increase the affinity of cationic pore blockers by establishing a local negative potential at the pore entrance; these charges modify channel gating by establishing a potential gradient across the ion channel; finally, both effects influence ion permeation through the pore. |
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