AC   MF_04104;
DC   Protein; auto
TR   HAMAP; MF_04104; -; 1; level=0
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Names: HOLIN_T4
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ID   HOLIN
DE   RecName: Full=Holin;
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CC   -!- FUNCTION: Accumulates harmlessly in the cytoplasmic membrane until it
CC       reaches a critical concentration that triggers the formation of micron-
CC       scale pores (holes) causing host cell membrane disruption and endolysin
CC       escape into the periplasmic space. Determines the precise timing of
CC       host cell lysis. Regulated by specific antiholins that somehow sense
CC       superinfections and then delay lysis. Participates with the endolysin
CC       and spanin proteins in the sequential events which lead to the
CC       programmed host cell lysis releasing the mature viral particles from
CC       the host cell.
CC   -!- SUBUNIT: Homomultimer. Heterotetramer composed of 2 holin and 2
CC       antiholin. The holin-antiholin complex binds dsDNA. Interacts (via C-
CC       terminus) with antiholin (via C-terminus); this interaction blocks the
CC       holin homomultimerization and delays host cell lysis. Interacts (via N-
CC       terminus) with the lysis inhibition accessory protein rIII; this
CC       interaction stabilizes the holin-antiholin complex thereby resulting in
CC       a robust block of the hole formation.
CC   -!- SUBCELLULAR LOCATION: Host cell inner membrane; Single-pass type II
CC       membrane protein; Periplasmic side. Note=Classified as a class III
CC       holin.
CC   -!- DOMAIN: The C-terminus serves, in association with the antiholin, as a
CC       DNA sensor for lysis inhibition under superinfection conditions.
case <FTTag:disulf>
CC   -!- PTM: Disulfide bond is required for functionality.
end case
CC   -!- SIMILARITY: Belongs to the T4likevirus holin family.
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DR   Pfam; PF11031; Phage_holin_T; 1; trigger=no
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KW   Cytolysis
case <FTTag:disulf>
KW   Disulfide bond
end case
KW   Host cell inner membrane
KW   Host cell lysis by virus
KW   Host cell membrane
KW   Host membrane
KW   Membrane
KW   Signal-anchor
KW   Transmembrane
KW   Transmembrane helix
KW   Viral release from host cell
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GO   GO:0140911; F:pore-forming activity
GO   GO:0016020; C:membrane
GO   GO:0020002; C:host cell plasma membrane
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FT   From: HOLIN_BPT4 (P06808)
FT   TOPO_DOM        Nter..34
FT                   /note="Cytoplasmic"
FT   TRANSMEM        35..49
FT                   /note="Helical; Signal-anchor for type II membrane protein"
FT   TOPO_DOM        50..Cter
FT                   /note="Periplasmic"
FT   DISULFID        175..207
FT   Tag: disulf; Condition: C-x*-C
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Size: 188-243;
Related: None;
Template: P06808;
Scope:
 Viruses; Caudoviricetes
Fusion:
 Nter: None
 Cter: None
Duplicate: None
Plasmid: None
Comments: None
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# Revision 1.9 2022/12/01
//