FIG 5.

Pore-forming activity of fonticins on black lipid membranes. (A) Example of one open membrane pore and gradual opening of five fonticin pores. With an increasing number of open pores, the current noise increases. The average single-pore conductance is 785 pS (histogram is shown in Fig. 6) measured in standard conditions (1 M NaCl, 10 mM Tris, and 8 mM MgCl₂, pH 7.3, with applied voltage of 50 mV). (B) Single-pore conductance of fonticins as a function of NaCl conductivity. Each point corresponds to a pore conductance measured in NaCl solution with increasing molar strength, specifically, 0.1, 0.25, 0.5, 0.75, 1, 1.5, 2, 2.5, and 3 M NaCl. For each NaCl concentration, a conductance histogram (n > 100) was constructed and fitted to a Gaussian function. The error bars represent the width at the half maximum of the Gaussian fit. The data points can be fitted to a straight line with a slope of 10.5 pS·cm·mS⁻¹. (C) Current-voltage characteristics of five fonticin channels that were simultaneously present in the membrane with 10-fold NaCl gradient. Ion selectivity for Na⁺ and Cl⁻ ions is 1:1 as can be deduced from the reversal potential where U_rev = −0.8 mV.