PMID:27825035

Citation	Fernandes, S and São-José, C (2017) Probing the function of the two holin-like proteins of bacteriophage SPP1. Virology 500:184-189
Abstract	Double-stranded DNA bacteriophages employ holin and endolysin functions to lyse host bacteria after virus multiplication. Holins oligomerize in the cytoplasmic membrane and trigger to form holes that cause cell death. For most systems these holes are also required for endolysin release to the cell wall, where it cleaves the peptidoglycan network. Orfs 25 and 26 of Bacillus subtilis phage SPP1 were predicted to encode the endolysin and holin functions, respectively. However, the product of the upstream orf 24.1 exhibits also holin features. We show that production of gp24.1 or gp26 in B. subtilis causes no major impact on cell growth, despite their ability to insert in the cytoplasmic membrane. Instant growth cessation and cell death is observed only upon co-production of the two holin-like proteins. Surprisingly, a constitutive promoter was identified within orf 24.1, which we propose to correspond to the previously described SPP1 early promoter PE5.
Links	PubMed Online version:10.1016/j.virol.2016.10.030
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
BPSPP:O48472		GO:0020002: host cell plasma membrane	ECO:0000314:		C		Figure 4 shows a SDS-Page analysis of the two gp24.1 and gp 26. The bands for gp 24.1 are shown under the Membrane section of the plate signifying that this gene is a membrane localized gene.	complete CACAO 12597
BPSPP:HOL24		GO:0020002: host cell plasma membrane	ECO:0000314:		C		In Figure 4, the membrane fraction column (M) of the Western blot panel (bottom row) for gp 24.1 shows that the holin-like protein of Bacillus phage SPP1 was detected at much higher levels in the cell membrane after cell fractionation, as opposed to the cytoplasm. Cell fractionation into cytoplasmic and membrane fractions followed by Western blot shows a thicker band of protein in the membrane fraction of the cells expressing gp24.1, with no band visible in the cytoplasmic fraction.	complete CACAO 12664
BPSPP:HOL24		GO:0033644: host cell membrane	ECO:0000315:		C		Figure 3C illustrates the alignment of nucleotide sequence of the early promoters PE1, PE2,and PE3 in comparison to that of PE5 in the SPP1 genome sequence. As the cell grows the B.subtilis in seen to not have an effect on its growth. The occurrence of holin had little effect on the development of the cell.	complete CACAO 12891
BPSPP:HOL24		GO:0039662: host cell outer membrane	ECO:0000314:		C		Bacillus phage SPP1 (Bacteriophage SPP1) holin-like protein 24.1 (gp24.1) As shown in Figure 4, the holin-like protein gp24.1 localizes to the cytosplasmic membrane.	complete

References

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