Summary: PPE family
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This family named after a PPE motif near to the amino terminus of the domain. The PPE family of proteins all contain an amino-terminal region of about 180 amino acids. The carboxyl terminus of this family are variable, and on the basis of this region fall into at least three groups. The MPTR subgroup has tandem copies of a motif NXGXGNXG. The second subgroup contains a conserved motif at about position 350. The third group are only related in the amino terminal region. The function of these proteins is uncertain but it has been suggested that they may be related to antigenic variation of Mycobacterium tuberculosis .
Cole ST, Brosch R, Parkhill J, Garnier T, Churcher C, Harris D, Gordon SV, Eiglmeier K, Gas S, Barry CE 3rd, Tekaia F, Badcock K, Basham D, Brown D, Chillingworth T, Connor R, Davies R, Devlin K, Feltwell T, Gentles S, Hamlin N, Holroyd S, Hornsby T, Jage, Nature 1998;393:537-544.: Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence. PUBMED:9634230 EPMC:9634230
Strong M, Sawaya MR, Wang S, Phillips M, Cascio D, Eisenberg D; , Proc Natl Acad Sci U S A. 2006;103:8060-8065.: Toward the structural genomics of complexes: crystal structure of a PE/PPE protein complex from Mycobacterium tuberculosis. PUBMED:16690741 EPMC:16690741
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR000030
The human pathogen Mycobacterium tuberculosis harbours a large number of genes that encode proteins whose N-termini contain the characteristic motifs Pro-Glu (PE) or Pro-Pro-Glu (PPE). A subgroup of the PE proteins contains polymorphic GC-rich sequences (PGRS), while a subgroup of the PPE proteins contains major polymorphic tandem repeats (MPTR). The function of most of these proteins remains unknown [PUBMED:19602151]. However, the PE_PGRS proteins from Mycobacterium marinum are secreted by components of the ESX-5 system that belongs to the recently defined type VII secretion systems [PUBMED:18981138]. It has also been reported that the PE_PGRS family of proteins contains multiple calcium-binding and glycine-rich sequence motifs GGXGXD/NXUX. This sequence repeat constitutes a calcium-binding parallel beta-roll or parallel beta-helix structure and is found in RTX toxins secreted by many Gram-negative bacteria [PUBMED:18267304].This mycobacterial family is named after a conserved amino-terminal region of about 180 amino acids, the PPE motif. The carboxy termini of proteins belonging to the PPE family are variable, and on the basis of this region at least three groups can be distinguished. The MPTR subgroup is characterised by tandem copies of a motif NXGXGNXG. The second subgroup contains a conserved motif at about position 350. The third group shares only similarity in the amino terminal region. The function of these proteins is uncertain but it has been suggested that they may be related to antigenic variation of Mycobacterium tuberculosis [PUBMED:9634230].
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The WXG100 protein secretion system (Wss) is responsible for the secretion of WXG100 proteins (PF06013), such as ESAT-10 (6 kDa early secreted antigenic target) and CFP-10 (10 kDa culture filtrate protein) in Mycobacterium tuberculosis or EsxA (ESAT-6-like extracellularly secreted protein A) and EsxB in Staphylococcus aureus. These two proteins, generally encoded in the same gene cluster, form a 1:1 heterodimeric complex. These proteins are virulence factors involved in host-pathogen interaction , as demonstrated in Mycobacterium tuberculosis, Staphylococcus aureus or Bacillus anthracis. The Wss is encoded in many other Gram-positive (monoderm) bacteria. This superfamily contains a number of DUFs which are closely related and may or may not represent the same family of proteins.
The clan contains the following 5 members:DUF2563 PE PPE T7SS_ESX_EspC WXG100
We make a range of alignments for each Pfam-A family:
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Curation and family details
|Seed source:||Pfam-B_297 (release 3.0)|
|Number in seed:||116|
|Number in full:||102566|
|Average length of the domain:||152.60 aa|
|Average identity of full alignment:||48 %|
|Average coverage of the sequence by the domain:||26.38 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 80369284 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||15|
|Download:||download the raw HMM for this family|
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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 PPE domain has been found. There are 6 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 seqence.
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