Summary: SRS domain
This is the Wikipedia entry entitled "SAG1 protein domain". More...
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SAG1 protein domain Edit Wikipedia article
|This article needs additional citations for verification. (August 2012)|
|Surface Antigen 1 (SAG1)|
Structure of the immunodominant epitope displayed by the Surface Antigen 1 (SAG1) of Toxoplasma gondii complexed to a monoclonal antibody.
In molecular biology, the SAG1 protein domain is an example of a group of glycosylphosphatidylinositol (GPI)-linked proteins named SRSs (SAG1 related sequence). SAG1 is found on the surface of a protozoan parasite Toxoplasma gondii. This parasite infects almost any warm-blooded vertebrate. The surface of T. gondii is coated with a family of developmentally regulated glycosylphosphatidylinositol (GPI)-linked proteins (SRSs), of which SAG1 is the prototypic member.
The structure of the immunodominant SAG1 antigen reveals a homodimeric configuration. This family of surface antigens is found in other apicomplexans. This particular antigen contains many cysteine residues which lead to disulphide bridge formation.
C terminal domain
This protein domain contains 120 amino acids.
There is a fold within this structure which is conserved amongst SRS proteins, and therefore named the SRS fold. The role of this fold is to aid the binding to cells, and promote infection within the host organism. The structure of this fold is analogous to the topology topology of the cupredoxin, azurin, a form of copper binding protein.
- He XL, Grigg ME, Boothroyd JC, Garcia KC (2002). "Structure of the immunodominant surface antigen from the Toxoplasma gondii SRS superfamily.". Nat Struct Biol 9 (8): 606–11. doi:10.1038/nsb819. PMID 12091874.
- Cesbron-Delauw MF, Tomavo S, Beauchamps P, Fourmaux MP, Camus D, Capron A et al. (1994). "Similarities between the primary structures of two distinct major surface proteins of Toxoplasma gondii.". J Biol Chem 269 (23): 16217–22. PMID 8206924.
- Swirnoff AH, Apel ED, Svaren J, Sevetson BR, Zimonjic DB, Popescu NC, Milbrandt J (January 1998). "Nab1, a corepressor of NGFI-A (Egr-1), contains an active transcriptional repression domain". Mol. Cell. Biol. 18 (1): 512–24. PMC 115883. PMID 9418898.
SRS domain Provide feedback
Toxoplasma gondii is a persistent protozoan parasite capable of infecting almost any warm-blooded vertebrate. The surface of Toxoplasma is coated with a family of developmentally regulated glycosylphosphatidylinositol (GPI)-linked proteins (SRSs), of which SAG1 is the prototypic member. SRS proteins mediate attachment to host cells and interface with the host immune response to regulate the virulence of the parasite. SAG1 is composed of two disulphide linked SRS domains. These have 6 cysteines that form 1-6,2-5 and 3-4 pairings. The structure of the immunodominant SAG1 antigen reveals a homodimeric configuration . The SRS domain is found in a single copy in the SAG2 proteins. This family of surface antigens are found in other apicomplexans.
Cesbron-Delauw MF, Tomavo S, Beauchamps P, Fourmaux MP, Camus D, Capron A, Dubremetz JF; , J Biol Chem 1994;269:16217-16222.: Similarities between the primary structures of two distinct major surface proteins of Toxoplasma gondii. PUBMED:8206924 EPMC:8206924
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR007226Toxoplasma gondii is a persistent protozoan parasite capable of infecting almost any warm-blooded vertebrate. The surface of T. gondii is coated with a family of developmentally regulated glycosylphosphatidylinositol (GPI)-linked proteins (SRSs), of which SAG1 is the prototypic member. SRS proteins mediate attachment to host cells and interface with the host immune response to regulate the virulence of the parasite. The structure of the immunodominant SAG1 antigen reveals a homodimeric configuration [PUBMED:9418898]. This family of surface antigens is found in other apicomplexans.
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Cellular component||membrane (GO:0016020)|
- the number of sequences which exhibit this architecture
a textual description of the architecture, e.g. Gla, EGF x 2, Trypsin.
This example describes an architecture with one
Gladomain, followed by two consecutive
EGFdomains, and finally a single
- the UniProt description of the protein sequence
- the number of residues in the sequence
- the Pfam graphic itself.
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We make a range of alignments for each Pfam-A family:
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Curation and family details
|Seed source:||Pfam-B_1675 (release 7.3)|
|Number in seed:||58|
|Number in full:||921|
|Average length of the domain:||131.00 aa|
|Average identity of full alignment:||20 %|
|Average coverage of the sequence by the domain:||67.81 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||8|
|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 SAG domain has been found. There are 14 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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