Holins: The Protein Clocks of Bacteriophage Infections

Abstract

Two proteins, an endolysin and a holin, are essential for host lysis by bacteriophage. Endolysin is the term for muralytic enzymes that degrade the cell wall; endolysins accumulate in the cytosol fully folded during the vegetative cycle. Holins are small membrane proteins that accumulate in the membrane until, at a specific time that is "programmed" into the holin gene, the membrane suddenly becomes permeabilized to the fully folded endolysin. Destruction of the murein and bursting of the cell are immediate sequelae. Holins control the length of the infective cycle for lytic phages and so are subject to intense evolutionary pressure to achieve lysis at an optimal time. Holins are regulated by protein inhibitors of several different kinds. Holins constitute one of the most diverse functional groups, with >100 known or putative holin sequences, which form >30 ortholog groups.

Surface-attached molecules control Staphylococcus aureus quorum sensing and biofilm development

“…The strategy we have developed is primarily useful for Gram-positive bacteria because they do not possess an outer membrane. Strategies for Gram-negative bacteria can be explored perhaps by exploiting surfaces coated with quorum-sensing-manipulation compounds together with molecules that form pores in the outer membrane such as holins, endolysins, or bacteriocins 50 . Likewise, surface-attached quorum-sensing molecules could be examined with other orthogonal approaches that exploit surface release of active compounds 22 .…”

Ecological and Evolutionary Benefits of Temperate Phage: What Does or Doesn't Kill You Makes You Stronger

“…However, during induction prophages which excise earliest can suppress the reproduction of co-infecting prophages, lysing the cell before their counterpart's lytic phage particles are fully assembled. [65] Thus, more trigger-happy prophages gain a reproductive advantage during lysis. [66,67] Such conflict over lysis timing could potentially drive a coevolutionary arms race for ever-more sensitive induction among co-infecting temperate phages.…”

Ecogenomics and genome landscapes of marine Pseudoalteromonas phage H105/1

“…Host lysis. Host lysis requires both a phage lysin and holin to dissolve the membrane potential and permeabilize the cell wall, respectively (Wang et al, 2000). ORF 50 contains a conserved domain of the Peptidase M15 Pfam family of metallopeptidases (Table 1), lysins likely involved in host cell lysis.…”