Summary

Ptu family

This family consists of toxic peptides that are isolated from the saliva of assassin bugs. The saliva contains a complex mixture of proteins that are used by the bug either to immobilise the prey or to digest it. One of the proteins (Ptu1) has been purified and shown to block reversibly the N-type calcium channels and to be less specific for the L- and P/Q- type calcium channels expressed in BHK cells [1].

Literature references

Bernard C, Corzo G, Mosbah A, Nakajima T, Darbon H; , Biochemistry 2001;40:12795-12800.: Solution structure of Ptu1, a toxin from the assassin bug Peirates turpis that blocks the voltage-sensitive calcium channel N-type. PUBMED:11669615

InterPro entry IPR012325

Assassin bugs (Arthropoda:Insecta:Hemiptera:Reduviidae), sometimes known as conenoses or kissing bugs, are one of the largest and morphologically diverse families of true bugs feeding on crickets, caterpillars and other insects. Some assassin bug species are bloodsucking parasites of mammals, even of human. They can be commonly found throughout most of the world and their size varies from a few millimetres to as much as 3 or 4 centimetres. The toxic saliva of the predatory assassin bugs contains a complex mixture of small and large peptides for diverse uses such as immobilizing and pre-digesting their prey, and defence against competitors and predators. Assassin bug toxins are small peptides with disulphide connectivity that target ion-channels. They are relatively homologous to the calcium channel blockers omega-conotoxins from marine cone snails and belong to the four-loop cysteine scaffold structural class PUBMED:11423127, PUBMED:11669615.

One of these small proteins, Ptu1, blocks reversibly the N-type calcium channels, but at the same time is less specific for the L- or P/Q-type calcium channels PUBMED:11423127. Ptu1 is 34 amino acid residues long and is cross-linked by three disulphide bridges. Ptu1 contains a beta-sheet region made of two antiparallel beta-strands and consists of a compact disulphide-bonded core from which four loops emerge as well as N- and C-termini PUBMED:11669615. Some assassin bug toxins are listed below:

Agriosphodrus dohrni (Assassin bug) toxin Ado1.
Isyndus obscurus (Assassin bug) toxin Iob1.
Peirates turpis (Assassin bug) toxin Ptu1.

Clan

This family is a member of clan Omega_toxin (CL0083), which contains the following 16 members:

Albumin_I Conotoxin Mu-conotoxin Omega-toxin Toxin_11 Toxin_12 Toxin_16 Toxin_18 Toxin_21 Toxin_22 Toxin_24 Toxin_27 Toxin_30 Toxin_7 Toxin_9 UPF0506

Gene Ontology

Cellular component	extracellular region (GO:0005576)
Molecular function	calcium channel inhibitor activity (GO:0019855)
Biological process	pathogenesis (GO:0009405)

External database links

PANDIT:	PF08117
SYSTERS:	Toxin_30

Domain organisation

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

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Alignments

There are various ways to view or download the sequence alignments that we store. You can use a sequence viewer to look at either the seed or full alignment for the family, or you can look at a plain text version of the sequence in a variety of different formats. More...

View options

Alignment:	Seed (2) Full (3) NCBI (2) Metagenomics (7)
Viewer:

Formatting options

Alignment:	Seed (2) Full (3)
Format:
Order:	Tree Alphabetical
Sequence:	Inserts lower case All upper case
Gaps:
Download/view:	Download View

Download options

Very large alignments can often cause problems for the formatting tool above. If you find that downloading or viewing a large alignment is problematic, you can also download a gzip-compressed, Stockholm-format file containing the seed or full alignment for this family.

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

The main seed and full alignments are generated using sequences from the UniProt sequence database. However, we also generate alignments using sequences from the NCBI sequence database and the "metaseq" metagenomics dataset.

You can view alignments from these two additional datasets using the form above, or you can download alignments of NCBI or metagenomics sequences, as gzip-compressed files.

Pfam alignments:	Seed (2) Full (3) NCBI (2) Metagenomics (7)
Full length sequences	Full-sequences (3)

External links

MyHits provides a collection of tools to handle multiple sequence alignments. For example, one can refine a seed alignment (sequence addition or removal, re-alignment or manual edition) and then search databases for remote homologs using HMMER2.

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...

Trees

This page displays the phylogenetic tree for this family. 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 or full alignments.

Note: You can also download the data files for the seed, full, NCBI or metagenomics trees.

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

Seed source:

Short protein clustering

Previous IDs:

none

Type:

Family

Author:

Lee SC

Number in seed:

2

Number in full:

3

Average length of the domain:

34.70 aa

Average identity of full alignment:

55 %

Average coverage of the sequence by the domain:

99.05 %

HMM information

HMM build commands:

build method: hmmbuild -o /dev/null HMM SEED

search method: hmmsearch -Z 9421015 -E 1000 HMM pfamseq

Model details:

Parameter	Sequence	Domain
Gathering cut-off	24.5	24.5
Trusted cut-off	24.9	79.1
Noise cut-off	24.2	23.5

Model length:

35

Family (HMM) version:

4

Download:

download the raw HMM for this family

Species distribution

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

Species trees

We show the species tree in one of two ways. For smaller trees we try to show an interactive representation, which allows you to select specific nodes in the tree and view them as an alignment or as a set of Pfam domain graphics.

Unfortunately we have found that there are problems viewing the interactive tree when the it becomes larger than a certain limit. Furthermore, we have found that Internet Explorer can become unresponsive when viewing some trees, regardless of their size. We therefore show a text representation of the species tree when the size is above a certain limit or if you are using Internet Explorer to view the site.

If you are using IE you can still load the interactive tree by clicking the "Generate interactive tree" button, but please be aware of the potential problems that the interactive species tree can cause.

Interactive tree

For all of the domain matches in a full alignment, we count the number that are found on all sequences in the alignment. This total is shown in the purple box.

We also count the number of unique sequences on which each domain is found, which is shown in green. Note that a domain may appear multiple times on the same sequence, leading to the difference between these two numbers.

Finally, we group sequences from the same organism according to the NCBI code that is assigned by UniProt, allowing us to count the number of distinct sequences on which the domain is found. This value is shown in the pink boxes.

We use the NCBI species tree to group organisms according to their taxonomy and this forms the structure of the displayed tree. Note that in some cases the trees are too large (have too many nodes) to allow us to build an interactive tree, but in most cases you can still view the tree in a plain text, non-interactive representation. Those species which are represented in the seed alignment for this domain are highlighted.

You can use the tree controls to manipulate how the interactive tree is displayed:

show/hide the summary boxes
highlight species that are represented in the seed alignment
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Structures

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 Toxin_30 domain has been found.

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Family: Toxin_30 (PF08117)

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