1.C.41 The Tripartite Haemolysin BL (HBL) Family
The HBL family includes a tipartite haemolysin from Bacillus cereus (Beecher and Wong 2000). 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 (Sastalla et al. 2013). 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 (Chen et al. 1996).
The generalized transport reaction catalyzed by HBL is:
Solutes (in) ⇌ solutes (out)