The diameter of water pores formed by colicin la in planar lipid bilayers

The effective size of colicin Ia channel was tested by a recently described method 9FEMS, Microbiology and Immunology (1992). 105: 93-100) in which the nonelectrolyte molecules with different hydrodynamic diameters (0.52 to 5.0nm) were used as molecular tools. We have shown that despite low conductance (55-105 pS at 1.5 MKCl, pH 7.0) the ion channels formed by colicin Ia have a fairly large water pore diameter equal to 1.66-1 1.88nm. The results are discussed in terms of an energetic barrier for ions passing into the channel lumen