This family consists of several enterobacterial haemolysin (HlyE) proteins.Hemolysin E (HlyE) is a novel pore-forming toxin of Escherichia coli, Salmonella typhi, and Shigella flexneri. HlyE is unrelated to the well characterised pore-forming E. coli hemolysins of the RTX family, haemolysin A (HlyA), and the enterohaemolysin encoded by the plasmid borne ehxA gene of E. coli 0157. However, it is evident that expression of HlyE in the absence of the RTX toxins is sufficient to give a hemolytic phenotype in E. coli. HlyE is a protein of 34 kDa that is expressed during anaerobic growth of E. coli. Anaerobic expression is controlled by the transcription factor, FNR, such that, upon ingestion and entry into the anaerobic mammalian intestine, HlyE is produced and may then contribute to the colonisation of the host [1].

1: E. coli hemolysin E (HlyE, ClyA, SheA): X-ray crystal structure of the toxin and observation of membrane pores by electron microscopy. Wallace AJ, Stillman TJ, Atkins A, Jamieson SJ, Bullough PA, Green J, Artymiuk PJ; Cell 2000;100:265-276. PMID:10660049