Journal of Bacteriology, November 2000, p. 6075-6081, Vol. 182, No. 21
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-21281; Institute of Microbiology and Genetics, Vienna Biocenter, University of Vienna, 1030 Vienna, Austria2; and VAGLAHS, Lipid Research, Los Angeles, California 900733
Received 2 May 2000/Accepted 28 July 2000
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
-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.
This article has been cited by other articles:
| Appl. Environ. Microbiol. | Infect. Immun. | Eukaryot. Cell |
|---|---|---|
| Mol. Cell. Biol. | J. Virol. | Microbiol. Mol. Biol. Rev. |
| ALL ASM JOURNALS |