PROSITE documentation PDOC00481
Hok/gef family cell toxic proteins signature


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.

Last update:

July 1998 / Pattern and text revised.


Technical section

PROSITE method (with tools and information) covered by this documentation:

HOK_GEF, PS00556; Hok/gef family cell toxic proteins signature  (PATTERN)


1AuthorsGerdes K. Poulsen L.K. Thisted T. Nielsen A.K. Martinussen J. Andreasen P.H.
TitleThe hok killer gene family in gram-negative bacteria.
SourceNew Biol. 2:946-956(1990).
PubMed ID2101633

2AuthorsBorodovsky M. Koonin E.V. Rudd K.E.
TitleNew genes in old sequence: a strategy for finding genes in the bacterial genome.
SourceTrends Biochem. Sci. 19:309-313(1994).
PubMed ID7940673

3AuthorsPoulsen L.K. Refn A. Molin S. Andersson P.
TitleTopographic analysis of the toxic Gef protein from Escherichia coli.
SourceMol. Microbiol. 5:1627-1637(1991).
PubMed ID1943700

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