Summary: Signal recognition particle, alpha subunit, N-terminal
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Signal recognition particle, alpha subunit, N-terminal Provide feedback
SRP is a complex of six distinct polypeptides and a 7S RNA that is essential for transferring nascent polypeptide chains that are destined for export from the cell to the translocation apparatus of the endoplasmic reticulum (ER) membrane . SRP binds hydrophobic signal sequences as they emerge from the ribosome, and arrests translation.
This tab holds annotation information from the InterPro database.
InterPro entry IPR007222
The signal recognition particle (SRP) is a multimeric protein, which along with its conjugate receptor (SR), is involved in targeting secretory proteins to the rough endoplasmic reticulum (RER) membrane in eukaryotes, or to the plasma membrane in prokaryotes [PUBMED:17622352, PUBMED:16469117]. SRP recognises the signal sequence of the nascent polypeptide on the ribosome. In eukaryotes this retards its elongation until SRP docks the ribosome-polypeptide complex to the RER membrane via the SR receptor [PUBMED:12605305]. Eukaryotic SRP consists of six polypeptides (SRP9, SRP14, SRP19, SRP54, SRP68 and SRP72) and a single 300 nucleotide 7S RNA molecule. The RNA component catalyses the interaction of SRP with its SR receptor [PUBMED:17507650]. In higher eukaryotes, the SRP complex consists of the Alu domain and the S domain linked by the SRP RNA. The Alu domain consists of a heterodimer of SRP9 and SRP14 bound to the 5' and 3' terminal sequences of SRP RNA. This domain is necessary for retarding the elongation of the nascent polypeptide chain, which gives SRP time to dock the ribosome-polypeptide complex to the RER membrane. In archaea, the SRP complex contains 7S RNA like its eukaryotic counterpart, yet only includes two of the six protein subunits found in the eukarytic complex: SRP19 and SRP54 [PUBMED:12364595].
The SR receptor is a monomer consisting of the loosely membrane-associated SR-alpha homologue FtsY, while the eukaryotic SR receptor is a heterodimer of SR-alpha (70 kDa) and SR-beta (25 kDa), both of which contain a GTP-binding domain [PUBMED:12654246]. SR-alpha regulates the targeting of SRP-ribosome-nascent polypeptide complexes to the translocon [PUBMED:10859309]. SR-alpha binds to the SRP54 subunit of the SRP complex. The SR-beta subunit is a transmembrane GTPase that anchors the SR-alpha subunit (a peripheral membrane GTPase) to the ER membrane [PUBMED:7844142]. SR-beta interacts with the N-terminal SRX-domain of SR-alpha, which is not present in the bacterial FtsY homologue. SR-beta also functions in recruiting the SRP-nascent polypeptide to the protein-conducting channel.
This entry represents the alpha subunit of the SR receptor.
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|Cellular component||signal recognition particle receptor complex (GO:0005785)|
|Molecular function||GTP binding (GO:0005525)|
|signal recognition particle binding (GO:0005047)|
|GTPase activity (GO:0003924)|
|Biological process||intracellular protein transport (GO:0006886)|
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|Seed source:||Pfam-B_7342 (release 7.3);|
|Author:||Wood V, Finn RD|
|Number in seed:||118|
|Number in full:||801|
|Average length of the domain:||253.40 aa|
|Average identity of full alignment:||21 %|
|Average coverage of the sequence by the domain:||41.17 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 26740544 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||12|
|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 SRP-alpha_N 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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