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Holin is a 105-amino-acid-residue cytoplasmic membrane protein with three transmembrane domains, naturally expressed by double-stranded lambada phage. Holin will oligomerize and form a hole on the inner membrane of host bacteria at a certain time at an allele-specific time. And then the formation of hole will help Endolysin, a kind of lysozyme, come out from cytoplasm to periplasm to degrade peptidoglycan and inhibit the respiration by eliminating proton gradient.
 
Holin is a 105-amino-acid-residue cytoplasmic membrane protein with three transmembrane domains, naturally expressed by double-stranded lambada phage. Holin will oligomerize and form a hole on the inner membrane of host bacteria at a certain time at an allele-specific time. And then the formation of hole will help Endolysin, a kind of lysozyme, come out from cytoplasm to periplasm to degrade peptidoglycan and inhibit the respiration by eliminating proton gradient.
  

Revision as of 01:46, 18 October 2014

Holin from lambda phage

Holin is a 105-amino-acid-residue cytoplasmic membrane protein with three transmembrane domains, naturally expressed by double-stranded lambada phage. Holin will oligomerize and form a hole on the inner membrane of host bacteria at a certain time at an allele-specific time. And then the formation of hole will help Endolysin, a kind of lysozyme, come out from cytoplasm to periplasm to degrade peptidoglycan and inhibit the respiration by eliminating proton gradient.

Sequence and Features


Assembly Compatibility:
  • 10
    COMPATIBLE WITH RFC[10]
  • 12
    COMPATIBLE WITH RFC[12]
  • 21
    COMPATIBLE WITH RFC[21]
  • 23
    COMPATIBLE WITH RFC[23]
  • 25
    COMPATIBLE WITH RFC[25]
  • 1000
    COMPATIBLE WITH RFC[1000]


Usage and Biology

Holin is a generic term to describe a group of small proteins produced by double-stranded DNA bacteriophage to trigger holes formation at the end of lytic cycle. In our project, we design our suicide switch based on the λ lysis model. The S holin, also called S105, encoded by S gene, a dual-start motif of λ phage, is an 105-amino-acid-residue CM protein with three transmembrane domains (TMD)[1]. S107, also called antiholin, is the other protein encoded by S gene, differing from the S holin only by the Met-Lys N-terminal extension. However, this difference confers to S107 an extra positive charge, which prevents its TMD1 from inserting into the CM[2]. Additionally, as its name suggests, S107 can bind to S105 and inhibit its function specifically[3]. In λ lysis system, S107 and S105 are encoded by S gene at ratio of approximately 1:2, which is defined by the two RNA structure, and if the amount of S107 is increased relative to S105, the 'lysis time' will be delayed[4]. The inhibition function of S107 can be subverted by collapsing proton motive force, which also allow insertion of TMD1 of S107 into CM, instantly increasing the amount of active holin by making previously inactive S107 - S105 complexes functional (Fig. 1).

Figure 1. The model for the membrane topology of S107 and S105. S105 consist of three transmembrane domains (TMD) with an N-out, C-in topology while S107 only has two TMDs, caused by an extra positive charge conferred by Lys2. The S107 can inhibit the function of S105, preventing it from forming holes in cell membrane. However, this inhibition can be subverted by the dissipation of proton motive force and in this case, S107 will become active holin, accelerating the rate of pore formation.

Reference

[1]Gründling, A., Bläsi, U., & Young, R. (2000). Biochemical and genetic evidence for three transmembrane domains in the class I holin, lambda S. Journal of Biological Chemistry, 275(2), 769-776.

[2]Young, R., Wang, I. N., & Roof, W. D. (2000). Phages will out: strategies of host cell lysis. Trends in microbiology, 8(3), 120-128.

[3]Bläsi, U., Chang, C. Y., Zagotta, M. T., Nam, K. B., & Young, R. (1990). The lethal lambda S gene encodes its own inhibitor. The EMBO journal, 9(4), 981.

[4]Bläsi, U., Nam, K., Hartz, D., Gold, L., & Young, R. (1989). Dual translational initiation sites control function of the lambda S gene. The EMBO journal, 8(11), 3501.