Binding to The Target Cell Surface Is The Crucial Step in Pore Formation of Hemolysin BL from Bacillus cereus
Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany
*
Author to whom correspondence should be addressed.
Toxins 2019, 11(5), 281; https://doi.org/10.3390/toxins11050281
Received: 18 April 2019 / Revised: 13 May 2019 / Accepted: 16 May 2019 / Published: 20 May 2019
(This article belongs to the Special Issue Pore-Forming Toxins (PFTs): Never Out of Fashion)
A major virulence factor involved in Bacillus cereus food poisoning is the three-component enterotoxin hemolysin BL. It consists of the binding component B and the two lytic components L1 and L2. Studying its mode of action has been challenging, as natural culture supernatants additionally contain Nhe, the second three-component enterotoxin, and purification of recombinant (r) Hbl components has been difficult. In this study, we report on pore-forming, cytotoxic, cell binding and hemolytic activity of recently generated rHbl components expressed in E. coli. It is known that all three Hbl components are necessary for cytotoxicity and pore formation. Here we show that an excess of rHbl B enhances, while an excess of rHbl L1 hinders, the velocity of pore formation. Most rapid pore formation was observed with ratios L2:L1:B = 1:1:10 and 10:1:10. It was further verified that Hbl activity is due to sequential binding of the components B - L1 - L2. Accordingly, all bioassays proved that binding of Hbl B to the cell surface is the crucial step for pore formation and cytotoxic activity. Binding of Hbl B took place within minutes, while apposition of the following L1 and L2 occurred immediately. Further on, applying toxin components simultaneously, it seemed that Hbl L1 enhanced binding of B to the target cell surface. Overall, these data contribute significantly to the elucidation of the mode of action of Hbl, and suggest that its mechanism of pore formation differs substantially from that of Nhe, although both enterotoxin complexes are sequentially highly related.
View Full-Text
▼
Show Figures
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
MDPI and ACS Style
Jessberger, N.; Dietrich, R.; Schwemmer, S.; Tausch, F.; Schwenk, V.; Didier, A.; Märtlbauer, E. Binding to The Target Cell Surface Is The Crucial Step in Pore Formation of Hemolysin BL from Bacillus cereus. Toxins 2019, 11, 281.
Show more citation formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.
- Supplementary File 1:
PDF-Document (PDF, 195 KB)