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1.C.41 The Tripartite Haemolysin BL (HBL) Family

The HBL family includes a tipartite haemolysin from Bacillus cereus. The three components are homologous but distantly related to each other. They are called HBL component B, HBL component L1 and HBL component L2. The toxin forms pores and has also been called the enterotoxic, necrotizing, vascular, permeability toxin, a likely virulence factor of B. cereus diarrheal food poisoning and necrotic infections. Two distinct sets of all three HBL components have been isolated from a single B. cereus isolate, MGBC145. Both exhibit haemolytic and vascular permeability activities, and the homologues could function interchangeably. In addition to B. cereus, a homologue, called Haemolysin YhlA has been isolated and characterized from Edwardsiella tarda.

The generalized transport reaction catalyzed by HBL is:

solutes (in) ⇌ solutes (out)

References associated with 1.C.41 family:

Beecher, D.J. and A.C.L. Wong (2000). Tripartite haemolysin BL: isolation and characterization of two distinct homologous sets of components from a single Bacillus cereus isolate. Microbiol. 146: 1371-1380. 10846215
Chen, J.D., S. Y. Lai and S.L. Huang (1996). Molecular cloning, characterization, and sequencing of the hemolysin gene from Edwardsiella tarda. Arch. Microbiol. 165: 9-17. 8639026
Fagerlund, A., T. Lindbäck, A.K. Storset, P.E. Granum, and S.P. Hardy. (2008). Bacillus cereus Nhe is a pore-forming toxin with structural and functional properties similar to the Cl- yA (HlyE, SheA) family of haemolysins, able to induce osmotic lysis in epithelia. Microbiology 154: 693-704. 18310016
Sastalla, I., R. Fattah, N. Coppage, P. Nandy, D. Crown, A.P. Pomerantsev, and S.H. Leppla. (2013). The Bacillus cereus Hbl and Nhe tripartite enterotoxin components assemble sequentially on the surface of target cells and are not interchangeable. PLoS One 8: e76955. 24204713
Zhu, K., A. Didier, R. Dietrich, U. Heilkenbrinker, E. Waltenberger, N. Jessberger, E. Märtlbauer, and R. Benz. (2015). Formation of small transmembrane pores: An intermediate stage on the way to Bacillus cereus non-hemolytic enterotoxin (Nhe) full pores in the absence of NheA. Biochem. Biophys. Res. Commun. [Epub: Ahead of Print] 26654951