PMID:11029427

Citation	Gründling, A, Smith, DL, Bläsi, U and Young, R (2000) Dimerization between the holin and holin inhibitor of phage lambda. J. Bacteriol. 182:6075-81
Abstract	Holins are integral membrane proteins that control the access of phage-encoded muralytic enzymes, or endolysins, to the cell wall by the sudden formation of an uncharacterized homo-oligomeric lesion, or hole, in the membrane, at a precisely defined time. The timing of lambda-infected cell lysis depends solely on the 107 codon S gene, which encodes two proteins, S105 and S107, which are the holin and holin inhibitor, respectively. Here we report the results of biochemical and genetic studies on the interaction between the holin and the holin inhibitor. A unique cysteine at position 51, in the middle of the second transmembrane domain, is shown to cause the formation of disulfide-linked dimers during detergent membrane extraction. Forced oxidation of membranes containing S molecules also results in the formation of covalently linked dimers. This technique is used to demonstrate efficient dimeric interactions between S105 and S107. These results, coupled with the previous finding that the timing of lysis depends on the excess of the amount of S105 over S107, suggest a model in which the inhibitor functions by titrating out the effector in a stoichiometric fashion. This provides a basis for understanding two evolutionary advantages provided by the inhibitor system, in which the production of the inhibitor not only causes a delay in the timing of lysis, allowing the assembly of more virions, but also increases effective hole formation after triggering.
Links	PubMed PMC94741
Keywords	Bacteriolysis; Bacteriophage lambda/chemistry; Bacteriophage lambda/metabolism; Cysteine/metabolism; Detergents; Dimerization; Disulfides; Time Factors; Viral Proteins/chemistry; Viral Proteins/genetics
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
LAMBD:VLYS	part_of	GO:0020002: host cell plasma membrane	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete
LAMBD:HOLIN	part_of	GO:0020002: host cell plasma membrane	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete
LAMBD:HOLIN		GO:0046983: protein dimerization activity	ECO:0000314:		F		Figure 2A. Shows Lambda Holin "S105" can dimerize.	complete CACAO 10445
LAMBD:HOLIN		GO:0020002: host cell plasma membrane	ECO:0000314:		C		Figure 3. shows dimer formation in the membrane. In methods - "soluble fractions of inner membrane proteins were prepared"	complete CACAO 10446

References

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