{PDOC00481}
{PS00556; HOK_GEF}
{BEGIN}
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* Hok/gef family cell toxic proteins signature *
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In Gram-negative bacteria there is a family of very small proteins which, when
overexpressed, kill the cells  from the  inside  by  interfering  with a vital
function in the cell membrane [1]. The proteins known to belong to this family
are:

 - Escherichia coli chromosomal protein gef.
 - Escherichia coli chromosomal protein relF.
 - Plasmid F protein flmA.
 - Plasmid F protein srnB.
 - Plasmid R1 protein hok.
 - Plasmids R16 and R483 protein pndA.
 - Escherichia coli hypothetical protein ybdY.
 - Escherichia coli hypothetical protein ydcB.
 - Escherichia coli hypothetical protein yiaZ [3].

These proteins  consist  of 49 to 68 amino acids.  Their N-terminal section is
hydrophobic and  seems  [3]  to form  a membrane-spanning region, while the C-
terminal part  is  located in  the  periplasm  and  contains the toxic domain.
Two cysteines  are conserved, one  in the N-terminal part and the other in the
C-terminal part;  in the gef protein, this second cysteine  has been shown [3]
to be involved in the formation of a disulfide bond between two monomers.

As a signature pattern we  selected the region  that  contains  the end of the
membrane-spanning region and ends with the second cysteine.

-Consensus pattern: [LIVMA](4)-C-[LIVMFA]-T-[LIVMA](2)-x(4)-[LIVM]-x-[RG]-
                    x(2)-L-[CY]
                    [The second C is involved in a disulfide bond]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: July 1998 / Pattern and text revised.

[ 1] Gerdes K., Poulsen L.K., Thisted T., Nielsen A.K., Martinussen J.,
     Andreasen P.H.
     "The hok killer gene family in gram-negative bacteria."
     New Biol. 2:946-956(1990).
     PubMed=2101633
[ 2] Borodovsky M., Koonin E.V., Rudd K.E.
     "New genes in old sequence: a strategy for finding genes in the
     bacterial genome."
     Trends Biochem. Sci. 19:309-313(1994).
     PubMed=7940673
[ 3] Poulsen L.K., Refn A., Molin S., Andersson P.
     "Topographic analysis of the toxic Gef protein from Escherichia
     coli."
     Mol. Microbiol. 5:1627-1637(1991).
     PubMed=1943700

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