PMID:21441511

Citation	Catalão, MJ, Gil, F, Moniz-Pereira, J and Pimentel, M (2011) Functional analysis of the holin-like proteins of mycobacteriophage Ms6. J. Bacteriol. 193:2793-803
Abstract	The mycobacteriophage Ms6 is a temperate double-stranded DNA (dsDNA) bacteriophage which, in addition to the predicted endolysin (LysA)-holin (Gp4) lysis system, encodes three additional proteins within its lysis module: Gp1, LysB, and Gp5. Ms6 Gp4 was previously described as a class II holin-like protein. By analysis of the amino acid sequence of Gp4, an N-terminal signal-arrest-release (SAR) domain was identified, followed by a typical transmembrane domain (TMD), features which have previously been observed for pinholins. A second putative holin gene (gp5) encoding a protein with a predicted single TMD at the N-terminal region was identified at the end of the Ms6 lytic operon. Neither the putative class II holin nor the single TMD polypeptide could trigger lysis in pairwise combinations with the endolysin LysA in Escherichia coli. One-step growth curves and single-burst-size experiments of different Ms6 derivatives with deletions in different regions of the lysis operon demonstrated that the gene products of gp4 and gp5, although nonessential for phage viability, appear to play a role in controlling the timing of lysis: an Ms6 mutant with a deletion of gp4 (Ms6(Δgp4)) caused slightly accelerated lysis, whereas an Ms6(Δgp5) deletion mutant delayed lysis, which is consistent with holin function. Additionally, cross-linking experiments showed that Ms6 Gp4 and Gp5 oligomerize and that both proteins interact. Our results suggest that in Ms6 infection, the correct and programmed timing of lysis is achieved by the combined action of Gp4 and Gp5.
Links	PubMed PMC3133122 Online version:10.1128/JB.01519-10
Keywords	Bacteriolysis; Cell Membrane/metabolism; Escherichia coli/enzymology; Gene Deletion; Mycobacteriophages/enzymology; Mycobacteriophages/genetics; Mycobacteriophages/physiology; Protein Binding; Protein Interaction Mapping; Protein Multimerization; Protein Structure, Tertiary; Sequence Analysis, DNA; Sequence Deletion; Viral Proteins/genetics; Viral Proteins/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
9VIRU:Q9G047	NOT	GO:1901217: regulation of holin activity	ECO:0000314:		P		"The one-step growth experiment (Fig. 7A) shows that Gp4 and Gp5, although nonessential for lysis, have an effect on the lysis timing since an Ms6 gp4 deletion mutant caused slightly accelerated lysis (80 min), whereas an Ms6 gp5 deletion mutant delayed lysis (170 min), which is consistent with holin function.These lysis times correspond to the latent time represented in Fig. 7A in addition to the initial 50 min of adsorption and were compared to the Ms6 wild-type phage (110 min) under the same experimental conditions. Thus, the absence of gp4 or gp5 in the infecting virion has an evident effect on the timing of lysis." "These results suggest that mycobacteriophage Ms6 gp4 and gp5 encode holin proteins whose combined action could play the role of a holin and that expression of both proteins is necessary to effect host cell lysis at the correct and programmed timing, as described for other phages such as the A. naeslundii phage Av-1 (3) and the B. subtilis PBSX phage (15)." "Moreover, interaction of Gp5 with Gp4 may contribute to very precise adjustment of the timing of hole formation and to keeping the infected cell productive, allowing the assembly of more virions." Quotes taken from paper itself. Particular attention should be given to Figure 7A as it takes	complete CACAO 11882
9VIRU:Q9G046	NOT	GO:1901217: regulation of holin activity	ECO:0000314:		P		"The one-step growth experiment (Fig. 7A) shows that Gp4 and Gp5, although nonessential for lysis, have an effect on the lysis timing since an Ms6 gp4 deletion mutant caused slightly accelerated lysis (80 min), whereas an Ms6 gp5 deletion mutant delayed lysis (170 min), which is consistent with holin function.These lysis times correspond to the latent time represented in Fig. 7A in addition to the initial 50 min of adsorption and were compared to the Ms6 wild-type phage (110 min) under the same experimental conditions. Thus, the absence of gp4 or gp5 in the infecting virion has an evident effect on the timing of lysis." "These results suggest that mycobacteriophage Ms6 gp4 and gp5 encode holin proteins whose combined action could play the role of a holin and that expression of both proteins is necessary to effect host cell lysis at the correct and programmed timing, as described for other phages such as the A. naeslundii phage Av-1 (3) and the B. subtilis PBSX phage (15)." "Moreover, interaction of Gp5 with Gp4 may contribute to very precise adjustment of the timing of hole formation and to keeping the infected cell productive, allowing the assembly of more virions." Quotes taken from paper itself. Particular attention should be given to Figure 7A as it takes	complete CACAO 11883

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