PMID:23335412

Citation	To, KH, Dewey, J, Weaver, J, Park, T and Young, R (2013) Functional analysis of a class I holin, P2 Y. J. Bacteriol. 195:1346-55
Abstract	Y is the putative holin gene of the paradigm coliphage P2 and encodes a 93-amino-acid protein. Y is predicted to be an integral membrane protein that adopts an N-out C-in membrane topology with 3 transmembrane domains (TMDs) and a highly charged C-terminal cytoplasmic tail. The same features are observed in the canonical class I lambda holin, the S105 protein of phage lambda, which controls lysis by forming holes in the plasma membrane at a programmed time. S105 has been the subject of intensive genetic, cellular, and biochemical analyses. Although Y is not related to S105 in its primary structure, its characterization might prove useful in discerning the essential traits for holin function. Here, we used physiological and genetic approaches to show that Y exhibits the essential holin functional criteria, namely, allele-specific delayed-onset lethality and sensitivity to the energization of the membrane. Taken together, these results suggest that class I holins share a set of unusual features that are needed for their remarkable ability to program the end of the phage infection cycle with precise timing. However, Y holin function requires the integrity of its short cytoplasmic C-terminal domain, unlike for S105. Finally, instead of encoding a second translational product of Y as an antiholin, as shown for lambda S107, the P2 lysis cassette encodes another predicted membrane protein, LysA, which is shown here to have a Y-specific antiholin character.
Links	PubMed PMC3592007 Online version:10.1128/JB.01986-12
Keywords	Amino Acid Sequence; Bacteriolysis; Bacteriophage P2/chemistry; Bacteriophage P2/genetics; Bacteriophage P2/metabolism; Membrane Proteins/chemistry; Membrane Proteins/genetics; Membrane Proteins/metabolism; Protein Structure, Tertiary; Viral Proteins/chemistry; Viral Proteins/genetics; Viral Proteins/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
BPP2:HOLIN		GO:0034291: canonical holin activity	ECO:0000314:		F		Figure 5	complete CACAO 10443
BPP2:HOLIN	enables	GO:0034291: canonical holin activity	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete
BPP2:HOLIN		GO:0034290: holin activity	ECO:0000314:		F		Figure 2 displays the results of expressing the holin gene in the lambda phage and testing its lysing abilities on E.coli. The activity assay shows that the holin reduces turbidity in the E.coli and thereby has the lytic properties of a holin.	complete CACAO 12892
BPP2:ANTIH		GO:1901218: negative regulation of holin activity	ECO:0000314:		P		Figure 4B shows the results of expressing the LysA gene on the activity of the Y holin. The incorporation of LysA resulted in a delay of the lysis activity of holin Y, thus indicating its negative regulation.	complete CACAO 12893

References

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