9.B.13 The Putative Pore-forming Entericidin (ECN) Family
&9;The ECN family includes two small lipoproteins, Entericidin B (a bacteriolytic toxin; 27 amino acyl residues) and Entericidin A (an anti-toxin antibiotic; 23 residues) in which the amino terminal cysteine is derivatized with an N-acyl-S-sn-1,2 diacyl glyceryl moiety. Both lipoproteins are predicted to adopt amphipathic α-helical structures in phospholipid bilayers and to thereby modulate membrane stability. These two small lipoproteins are tandemly encoded in the ecn locus of the E. coli chromosome; their syntheses are induced in stationary phase, and they mediate programmed cell death of a subpopulation of the bacteria. It is possible that Entericidin B exerts its toxic effect by forming transmembrane pores, but this possibility has not been established.