"listeria monocytogenes" bacteriophage a118 encodes a native holin, hol118, of 93 amino acyl residues (aas) exhibiting 3 putative transmembrane segments (tmss). when cloned into lambda phage devoid of the s holin, it caused very late cell lysis, beginning 80 min. after induction. hol118 appeared in the cytoplasmic membrane shortly after infection. a second translational start codon (aug-3) at nucleotide position 40 in the gene gives rise to a second gene product of 83 aas lacking tms-1 (hol118(83)). it is produced with the full length protein, appears in the membrane, but cannot support lambda lysis and inhibits lysis by hol118. this dominant inhibitor presumably determines the time of lysis. a homologue is found in "l. innocua."