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1.C.60 The Two-component Enterococcus faecalis Cytolysin (EFC) Family

The EFC family includes a single member, the cytolysin of E. faecalis which consists of two subunits, CylL (large; 68 aas) and CylL (small; 63 aas). They are post-transcriptionally modified by CylM and secreted by the ABC exporter, CylB (TC #3.A.1.111.1). Extracellularly, the two subunits are activated by a protease, CylA yielding the functional mature cytolysin subunits, CylL"L and CylL"S. CylI confers protection to the producer.

The cytolysin is a "pseudohaemolysin" which produces hemolysis on blood agar plates, but not in broth culture. This may be due to regulated synthesis of the cytolysin by an unusual two-component system that senses the extracellular concentration of an inducer via a quorum sensing autoinduction mechanism (Haas et al., 2002). In addition to its toxicity to animal cells, it is bacteriocidal for nearly all Gram-positive bacteria.

References associated with 1.C.60 family:

Haas, W., B.D. Shepard, and M.S. Gilmore. 2002. Two-component regulator of Enterococcus faecalis cytolysin responds to quorum-sensing autoinduction. Nature 415: 84-86. 11780122
Hällgren, A., C. Claesson, B. Saeedi, H.J. Monstein, H. Hanberger, and L.E. Nilsson. (2009). Molecular detection of aggregation substance, enterococcal surface protein, and cytolysin genes and in vitro adhesion to urinary catheters of Enterococcus faecalis and E. faecium of clinical origin. Int. J. Med. Microbiol. 299: 323-332. 19042153