Porin function of purified PomS.

<p>Single channel experiments using a PC/<i>n</i>-decane membrane in the presence of purified PomS. The aqueous phase contained 1 M KCl and 10 ng ml⁻¹ PomS dissolved in 1% Genapol. The applied membrane potential was 20 mV; T = 20°C. Left panel: Single-channel recordings show a uniform stepwise increase as expected for a highly enriched purified porin. Right panel: Frequency of observed conductance increments. P(G) was calculated by dividing the number of fluctuations with a given conductance increment by the total number of conductance fluctuations. Data from both panels suggest that the purified protein fraction contains mainly PomS (about 82% of the total number of pores) and that there is only a very minor contribution of other pores in the histogram (about 18% of the total number of pores) caused either by contaminant porins or by degradation of PomS. The average single-channel conductance was 3.25 nS for 230 single-channel events.