OPTICAL SINGLE-CHANNEL ANALYSIS OF THE AEROLYSIN PORE IN ERYTHROCYTE-MEMBRANES

Scanning microphotolysis (Scamp), a recently developed photobleaching technique, was used to analyze the transport of two small organic anio ns and one inorganic cation through single pores formed in human eryth rocyte membranes by the channel-forming toxin aerolysin secreted by Ae romonas species. The transport rate constants of erythrocyte ghosts ca rrying a single aerolysin pore were determined to be (1.83 +/- 0.43) x 10(-3) s(-1) for Lucifer yellow, (0.33 +/- 0.10) x 10(-3) s(-1) for c arboxyfluorescein, and (8.20 +/- 2.30) x 10(-3) s(-1) for Ca2+. The ra dius of the aerolysin pore was derived from the rate constants to be 1 9-23 Angstrom, taking steric hindrance and viscous drag into account. The size of the Ca2+ rate constant implies that at physiological extra cellular Ca2+ concentrations (>1 mM) the intracellular Ca2+ concentrat ion would be elevated to the critical level of >1 mu M in much less th an a second after formation of a single aerolysin pore in the plasma m embrane. Thus changes in the levels of Ca2+ or other critical intracel lular components may be more likely to cause cell death than osmotic i mbalance.