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9  structures 774  species 0  interactions 1120  sequences 4  architectures

Family: RelE (PF06296)

Summary: RelE toxin of RelE / RelB toxin-antitoxin system

Pfam includes annotations and additional family information from a range of different sources. These sources can be accessed via the tabs below.

This is the Wikipedia entry entitled "Toxin-antitoxin system". More...

Toxin-antitoxin system Edit Wikipedia article

A toxin-antitoxin system is a plasmid stabilisation mechanism found in many prokaryotes.[1] Chromosomal toxin-antitoxin systems also exist and serve to respond to stresses, cause cell cycle arrest and bring about programmed cell death.[2] The systems involve a toxic protein which is inhibited via either a non-coding RNA (type I toxin-antitoxin) or by another protein (type II toxin-antitoxin).

Type I toxin-antitoxin system

Type II toxin antitoxin system

See also


  1. ^ Fozo EM, Makarova KS, Shabalina SA, Yutin N, Koonin EV, Storz G (2010). "Abundance of type I toxin-antitoxin systems in bacteria: searches for new candidates and discovery of novel families". Nucleic Acids Res. 38 (11): 3743–59. doi:10.1093/nar/gkq054. PMC 2887945. PMID 20156992. Retrieved 2010-08-11. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  2. ^ Hayes F (2003). "Toxins-antitoxins: plasmid maintenance, programmed cell death, and cell cycle arrest". Science. 301 (5639): 1496–9. doi:10.1126/science.1088157. PMID 12970556. Retrieved 2010-08-11. {{cite journal}}: Unknown parameter |month= ignored (help)


Further Reading

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.

RelE toxin of RelE / RelB toxin-antitoxin system Provide feedback

RelE is a family of Gram-negative bacterial antitoxins of the RelE/RelB toxin-antitoxin system. Its cognate antitoxin is family RelB, PF04221.

Literature references

  1. Francuski D, Saenger W;, J Mol Biol. 2009;393:898-908.: Crystal structure of the antitoxin-toxin protein complex RelB-RelE from Methanococcus jannaschii. PUBMED:19712680 EPMC:19712680

  2. Li GY, Zhang Y, Inouye M, Ikura M;, J Biol Chem. 2009;284:14628-14636.: Inhibitory mechanism of Escherichia coli RelE-RelB toxin-antitoxin module involves a helix displacement near an mRNA interferase active site. PUBMED:19297318 EPMC:19297318

  3. Shinohara M, Guo JX, Mori M, Nakashima T, Takagi H, Nishimoto E, Yamashita S, Tsumoto K, Kakuta Y, Kimura M;, Biochem Biophys Res Commun. 2010;400:346-351.: The structural mechanism of the inhibition of archaeal RelE toxin by its cognate RelB antitoxin. PUBMED:20728434 EPMC:20728434

Internal database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR009387

Bacterial toxin-antitoxin loci consist of two genes in an operon encoding a 'toxin' and an 'antitoxin' respectively. Ectopic expression of the toxins severely reduces cell growth and prevents colony formation. This entry includes HigB-2, one of the toxins found in Vibrio cholerae. It inhibits translation by cleavage of mRNA [ PUBMED:17085558 , PUBMED:17020579 ].

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Pfam Clan

This family is a member of clan Plasmid-antitox (CL0136), which has the following description:

The families in this clan are plasmid encoded anti-toxins involved in plasmid maintenance. The plasmid encodes both a toxin and an antitoxin. Upon loss of the plasmid the antitoxin is inactivated more rapidly than the toxin. This allows the toxin to interact with its target thus killing the cell or impeding growth.

The clan contains the following 16 members:

BrnT_toxin DUF2281 DUF4258 Gp49 HigB-like_toxin MqsR_toxin ParE-like_toxin ParE_toxin PHD_like PhdYeFM_antitox REGB_T4 RelE Toxin_YhaV TrmO_C YafQ_toxin YoeB_toxin


We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database (reference proteomes) using the family HMM. We also generate alignments using four representative proteomes (RP) sets and the UniProtKB sequence database. More...

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We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.

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Representative proteomes UniProt

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We make all of our alignments available in Stockholm format. You can download them here as raw, plain text files or as gzip-compressed files.

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You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

HMM logo

HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...


This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.

Note: You can also download the data file for the tree.

Curation and family details

This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.

Curation View help on the curation process

Seed source: Pfam-B_12045 (release 9.0)
Previous IDs: DUF1044;
Type: Domain
Sequence Ontology: SO:0000417
Author: Moxon SJ
Number in seed: 19
Number in full: 1120
Average length of the domain: 103.8 aa
Average identity of full alignment: 25 %
Average coverage of the sequence by the domain: 90.55 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 61295632 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 27.0 27.0
Trusted cut-off 27.0 27.0
Noise cut-off 26.9 26.9
Model length: 120
Family (HMM) version: 15
Download: download the raw HMM for this family

Species distribution

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Colour assignments

Archea Archea Eukaryota Eukaryota
Bacteria Bacteria Other sequences Other sequences
Viruses Viruses Unclassified Unclassified
Viroids Viroids Unclassified sequence Unclassified sequence


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This visualisation provides a simple graphical representation of the distribution of this family across species. You can find the original interactive tree in the adjacent tab. More...

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The tree shows the occurrence of this domain across different species. More...


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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the RelE domain has been found. There are 9 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein sequence.

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AlphaFold Structure Predictions

The list of proteins below match this family and have AlphaFold predicted structures. Click on the protein accession to view the predicted structure.

Protein Predicted structure External Information
A0A0H3GV41 View 3D Structure Click here
Q329F3 View 3D Structure Click here
Q8ZL23 View 3D Structure Click here
Q9KMA6 View 3D Structure Click here