THE DIAMETER OF WATER PORES FORMED BY COLICIN IA IN PLANAR LIPID BILAYERS

The effective size of colicin Ia channel was tested by a recently desc ribed method (FEMS, Microbiology and Immunology (1992). 105: 93-100) i n which the nonelectrolyte molecules with different hydrodynamics diam eters (0.52 to 5.0 nm) were used as molecular tools. We have shown tha t despite low conductance (55-105 pS at 1.5 M KCl, pH 7.0) the ion cha nnels formed by colicin Ia have a fairly large water pore diameter equ al to 1.66-1.88 nm. The results are discussed in terms of an energetic barrier for ions passing into the channel lumen.