INTERACTION OF SERRATIA-MARCESCENS HEMOLYSIN (SHLA) WITH ARTIFICIAL AND ERYTHROCYTE-MEMBRANES - DEMONSTRATION OF THE FORMATION OF AQUEOUS MULTISTATE CHANNELS

Pore formation by hemolysin (ShlA) of Serratia marcescens was studied in erythrocytes and in artificial lipid bilayer membranes. The results with erythrocytes demonstrated that hemolysin pores varied in size. I n erythrocyte membranes with reduced fluidity (0 degrees C), the toxin formed small pores with diameter 1-1.5 nm. In fluid membranes (above 20 degrees C), hemolysin pores with larger diameters (approximately 2. 5-3.0 nm) were observed, which may be caused by association of ShlA mo nomers into oligomers. Comparison of the channels formed by Staphyloco ccus aureus alpha-toxin with channels formed by ShlA indicated a sligh tly smaller pore diameter of ShlA pores. Analysis of ShlA in artificia l lipid bilayers showed the formation of pores with a broad distributi on of single channel conductances, suggesting variable sizes of the Sh lA pore. The lower limit for the pore diameter was approximately 1.0 n m. The ShlA pores did not exhibit pronounced ion selectivity nor volta ge dependence, supporting the presence of a large water-filled pore.