Structural and Functional Investigation of the Ag(+)/Cu(+) Binding Domains of the Periplasmic Adaptor Protein SilB from Cupriavidus metallidurans CH34.

Silver ion resistance in bacteria mainly relies on efflux systems, and notably on tripartite efflux complexes involving a transporter from the resistance-nodulation-cell division (RND) superfamily, such as the SilCBA system from Cupriavidus metallidurans CH34. The periplasmic adaptor protein SilB hosts two specific metal coordination sites, located in the N-terminal and C-terminal domains, respectively, that are believed to play a different role in the efflux mechanism and the trafficking of metal ions from the periplasm to the RND transporter. On the basis of the known domain structure of periplasmic adaptor proteins, we designed different protein constructs derived from SilB domains with either one or two metal binding sites per protein chain.

Unexpected wide substrate specificity of C. perfringens α-toxin phospholipase C.

Clostridium perfringens phospholipase C (CpPLC), also called α-toxin, is the main virulence factor for gas gangrene in humans. The lipase activity serves the bacterium to generate lipid signals in the host eukaryotic cell, and ultimately to degrade the host cell membranes. Several previous reports indicated that CpPLC was specific for phosphatidylcholine and sphingomyelin.

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

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.

Phospholipase C and sphingomyelinase activities of the Clostridium perfringens alpha-toxin.

Alpha-toxin is a major pathogenic determinant of Clostridium perfringens, the causative agent of gas gangrene. Alpha-toxin has been known for long to be a phospholipase C, but up to now its hydrolytic properties have been studied only through indirect methods, e.g.

Alkanes are not innocuous vehicles for hydrophobic reagents in membrane studies.

Alkanes (C6-C16) are often used as vehicles for hydrophobic reagents, e.g. long-chain ceramides, in cell biology studies.