Effects of surface charge on the conductance of the gramicidin channel.

The electric conductance of the cation-permeable gramicidin channel in negatively charged phosphatidylserine membranes has been studied. At low electrolyte concentrations the single-channel conductance is much larger in the negatively charged membrane than in a neutral membrane. This enhancement of conductance is in agreement with theoretical expectations, although a complete description of the salt concentration dependence of conductance was not possible. The results of these experiments may be compared with previous studies of a negatively charged gramicidin analog (O-pyromellityl gramicidin). It is found that the electrostatic effect on the conductance is much larger for a neutral channel embedded in a negatively charged lipid than for the negatively charged O-pyromellityl analog (with three charges at the channel mouth) embedded in a neutral lipid.