Effects of bilayer composition and physical properties on the phospholipase C and sphingomyelinase activities of Clostridium perfringens α-toxin

• Published in: Biochimica et biophysica acta Vol. 1808; no. 1; pp. 279 - 286
• Main Authors: Urbina, Patricia, Flores-Díaz, Marietta, Alape-Girón, Alberto, Alonso, Alicia, Goñi, Félix M.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-01-2011
• Subjects: Bacterial Toxins - chemistry; Calcium-Binding Proteins - chemistry; Cholesterol; Cholesterol - chemistry; Clostridium perfringens; Escherichia coli - metabolism; Gangliosides - chemistry; Hydrogen-Ion Concentration; Light; Lipid Bilayers - chemistry; Lipid curvature; Lipid negative charge; Lipids - chemistry; Lysophospholipids - chemistry; Lysosomal lipids; Phosphates - chemistry; Phospholipase C; Recombinant Proteins - chemistry; Scattering, Radiation; Sphingomyelin Phosphodiesterase - chemistry; Sphingomyelinase; Type C Phospholipases - chemistry; DOPE; Chol; DOPG; BMP; LBPA; PLC; DOPS; Cholesterol; Clostridium perfringens; SMase; Phospholipase C; BSA; Lipid curvature; PI; DOPA; Sphingomyelinase; Lipid negative charge; DOPC; Lysosomal lipids
• ISSN: 0005-2736; 0006-3002; 1879-2642
• DOI: 10.1016/j.bbamem.2010.08.011

α-Toxin, a major determinant of Clostridium perfringens toxicity, exhibits both phospholipase C and sphingomyelinase activities. Our studies with large unilamellar vesicles containing a variety of lipid mixtures reveal that both lipase activities are enhanced by cholesterol and by lipids with an intrinsic negative curvature, e.g. phosphatidylethanolamine. Conversely lysophospholipids, that possess a positive intrinsic curvature, inhibit the α-toxin lipase activities. Phospholipids with a net negative charge do not exert any major effect on the lipase activities, and the same lack of effect is seen with the lysosomal lipid bis (monoacylglycero) phosphate. Ganglioside GT1b has a clear inhibitory effect, while the monosialic ganglioside GM3 is virtually ineffectual even when incorporated at 6mol % in the vesicles. The length of the lag periods appears to be inversely related to the maximum (post-lag) enzyme activities. Moreover, and particularly in the presence of cholesterol, lag times increase with pH. Both lipase activities are sensitive to vesicle size, but in opposite ways: while phospholipase C is higher with larger vesicles, sphingomyelinase activity is lower. The combination of our results with previous structural studies suggests that α-toxin lipase activities have distinct, but partially overlapping and interacting active sites.
► α-Toxin, a major determinant of Clostridium perfringens toxicity, exhibits both phospholipase C and sphingomyelinase activities. ► Both activities are enhanced by cholesterol and by phospholipids with intrinsic negative curvatures, and inhibited by lipids with positive intrinsic curvatures. ► Phospholipids with a net negative charge in the headgroup do not exert any marked effects on the lipase activities. ► Sphingomyelinase activity decreases with increasing vesicle diameter, while phospholipase C activity increases with increasing vesicle size. ► The two lipase activities in the toxin appear to have distinct, but partially overlapping and interacting active sites.