Send to

Choose Destination
Biochemistry. 1995 May 16;34(19):6513-20.

Interaction of theta-toxin (perfringolysin O), a cholesterol-binding cytolysin, with liposomal membranes: change in the aromatic side chains upon binding and insertion.

Author information

Department of Enzyme Biochemistry and Membrane Biochemistry, Tokyo Metropolitan Institute of Gerontology, Japan.


To understand the mechanism of membrane lysis by theta-toxin (perfringolysin O) from Clostridium perfringens, a cholesterol-binding, pore-forming cytolysin, we undertook a spectroscopic analysis of the structural changes that occur during the lytic process using lipid vesicles. In particular, the spectra were compared with those obtained using a modified theta-toxin, MC theta, that binds membrane cholesterol without forming oligomeric pores, thus bypassing the oligomerization step. The interaction of theta-toxin with liposomes composed of cholesterol and phosphatidylcholine but not with cholesterol-free liposomes caused a remarkable increase in the intensity of the tryptophan fluorescence emission spectra and ellipticity changes in the near- and far-UV CD peaks. A CD peak shift from 292 to 300 nm was specific for theta-toxin, suggesting oligomerization-specific changes occurring around tryptophan residues. Structural changes in the aromatic side chains were detected in the near-UV CD and fluorescence spectra upon MC theta-liposome interaction, although the far-UV CD spectra indicate that the beta-rich secondary structure of MC theta is well-conserved after membrane binding. Quenching of the intrinsic tryptophan fluorescence of MC theta by brominated lecithin/cholesterol liposomes suggests that theta-toxin inserts at least partly into membranes in the absence of oligomerization. These results indicate that regardless of oligomerization, the binding of theta-toxin to cholesterol induces partial membrane insertion and triggers conformational changes accompanied by aromatic side chain rearrangement with retention of secondary structure.(ABSTRACT TRUNCATED AT 250 WORDS).

[Indexed for MEDLINE]

Supplemental Content

Loading ...
Support Center