1.E.21 The Listeria Phage A118 Holin (Hol118) Family

Listeria monocytogenes bacteriophage A118 encodes a native holin, hol118, of 93 aas exhibiting 3 putative TMS. When cloned into lambda (λΔSthf) devoid of the S holin, it caused very late cell lysis, beginning 80 min. after induction (Vukov et al., 2003). 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 TMS1 (Hol118(83)). It is produced with the full length protein, appears in the membrane, cannot support lambda lysis, and inhibits lysis by Hol118. This dominant inhibitor presumably determines the time of lysis (Vukov et al., 2003). A homologue is found in L. innocua.

The reaction probably catalyzed is:

small molecules + autolysin (in) → small molecules + autolysin (out)