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PMID:11018145
| Citation |
Wang, IN, Smith, DL and Young, R (2000) Holins: the protein clocks of bacteriophage infections. Annu. Rev. Microbiol. 54:799-825 |
|---|---|
| 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. |
| Links |
PubMed Online version:10.1146/annurev.micro.54.1.799 |
| Keywords |
Amino Acid Sequence; Bacteriolysis/physiology; Bacteriophages/growth & development; Biological Clocks; Coliphages/growth & development; Endopeptidases/metabolism; Lysogeny; Membrane Proteins/metabolism; Molecular Sequence Data; Siphoviridae/growth & development; Viral Proteins/metabolism |
Significance
Annotations
| Gene product | Qualifier | GO Term | Evidence Code | with/from | Aspect | Extension | Notes | Status |
|---|---|---|---|---|---|---|---|---|
| GO:0020002: host cell plasma membrane |
ECO:0000315: |
C |
Figure 1: Lysis requires the genes S and R. R codes for endolysin. S codes for the holin and holin inhibitor (genes 105 and 107) in Lambda. Lambda phages were mutated to be either without the holin gene (S), and with the endolysin (R) gene (or vice versa) or with both holin and endolysin gene. And as seen in the image, the lambda phages without the S gene did not lyse. However, the lambda phages with out R did lyse, at about 60 minuets. And the Lambda phage with both lysed at 40 minuets, which was the quickest lyse without the help of methyl trichloride. This suggests that endolysin is not required for lysis but involved in cleaving the bonds in the peptidoglycan. |
complete | ||||
Notes
See also
References
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