Inhibition of cytotoxicity by the Nhe cytotoxin of Bacillus cereus through the interaction of dodecyl maltoside with the NheB component.

Danh Phung, Per Einar Granum, Richard Dietrich, Erwin Märtlbauer, Simon P Hardy

Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, Oslo, Norway.

FEMS microbiology letters 2012 May

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Nhe ('nonhaemolytic enterotoxin') is a three-component cytotoxin implicated in the pathogenesis of diarrhoea by Bacillus cereus. Nhe forms pores in pure lipid bilayers, but the function of the individual components (NheA, NheB and NheC) remains unclear. NheB and NheC are structural homologues of ClyA, a pore-forming cytotoxin of Escherichia coli. The non-ionic detergent dodecyl maltoside (DDM) has been shown to inhibit haemolysis of ClyA. We used DDM as a probe to examine the response of the Nhe proteins to DDM micelles. At its critical micellar concentration (0.2 mM), DDM inhibited propidium uptake by the native Nhe complex in Vero and HT29 cell suspensions. Pre-incubation of NheC with DDM did not inhibit cytotoxicity. NheB exhibited marked changes in 1-anilinonaphthalene-8-sulphonic acid (ANS) fluorescence after pre-exposure to DDM. Pre-incubation of NheB with DDM resulted in large molecular weight complexes as detected by size exclusion chromatography and diffusion through sized dialysis membranes and prevented binding of NheB to Vero cell monolayers. These data support a model in which conformational changes and oligomerization of NheB are prerequisite events in the process of pore formation. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Citation

Danh Phung, Per Einar Granum, Richard Dietrich, Erwin Märtlbauer, Simon P Hardy. Inhibition of cytotoxicity by the Nhe cytotoxin of Bacillus cereus through the interaction of dodecyl maltoside with the NheB component. FEMS microbiology letters. 2012 May;330(2):98-104