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3.A.5.9.1
Sec-SRP translocase complex. The BAP29 and BAP31 (also called BCAP31) proteins interact directly with the Sec translocon (Wilson & Barlowe et al., 2010).  SRP68 and SRP72 form a complex with SRP RNA and SRP19.  The SRP68 binding site for the RNA is a tetratricopeptide-like module that bends the RNA and inserts an arginine-rich helix into the major groove to open the conserved 5f RNA loop and remodel the RNA for protein translocation (Grotwinkel et al. 2014).  Sec31 (Sec 31L1; HSPC334; HSPC275) is an outer cage component of the coat protein complex II (COPII) machinery which is recruited to specialized regions of the ER, called ER exit sites (ERES), where it plays a central role in the early secretory pathway. Sec31 also interacts with ALG-2 (Programed cell death protein 6 (PDCD6)) and annexin A11 (AnxA11) (Shibata et al. 2015). The Sec61 translocon mediates poorly efficient membrane insertion of Arg-containing TMSs, but a combination of arginine snorkeling, bilayer deformation, and peptide tilting is sufficient to lower the penalty of Arg insertion to an extent that a hydrophobic TMS with a central Arg residue readily inserts into a membrane (Ulmschneider et al. 2017). Mycolactone is a bacterium-derived macrolide that blocks the biogenesis of a large array of secretory and integral transmembrane proteins through potent inhibition of the Sec61 translocon (Morel et al. 2018). The Sec61α subunit possesses an opening between TMS2b and TMS7, the lateral gate, that is the exit for signal sequences and TMSs of translocating polypeptides to the lipid bilayer (Kida and Sakaguchi 2018). BCAP31 (BAP31; 246 aas and 3 N-terminal TMSs) is an ER chaparone that plays a role in the export of secreted proteins in the ER as well as the recognition of abnormally folded protein for targeting to the ER associated-degradation (ERAD) pathway (Wakana et al. 2008). It also serves as a cargo receptor for the export of transmembrane proteins (Annaert et al. 1997). Sec61 is the target of the cytotoxic plant-derived compound, ipomoeassin F (see TC family 8.C.10).

Accession Number:P49458
Protein Name:Signal recognition particle 9 kDa protein aka SRP9
Length:86
Molecular Weight:10112.00
Species:Homo sapiens (Human) [9606]
Location1 / Topology2 / Orientation3: Cytoplasm1
Substrate protein polypeptide chain

Cross database links:

DIP: DIP-6151N
RefSeq: NP_003124.1    XP_001720178.1   
Entrez Gene ID: 653226    6726   
Pfam: PF05486   
OMIM: 600707  gene
KEGG: hsa:653226   

Gene Ontology

GO:0005785 C:signal recognition particle receptor complex
GO:0005786 C:signal recognition particle, endoplasmic re...
GO:0008312 F:7S RNA binding
GO:0005515 F:protein binding
GO:0005047 F:signal recognition particle binding
GO:0045900 P:negative regulation of translational elonga...
GO:0006614 P:SRP-dependent cotranslational protein targe...

References (3)

[1] “Human signal recognition particle (SRP) Alu-associated protein also binds Alu interspersed repeat sequence RNAs. Characterization of human SRP9.”  Hsu K.et.al.   7730321
[2] “The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).”  The MGC Project Teamet.al.   15489334
[3] “Lysine acetylation targets protein complexes and co-regulates major cellular functions.”  Choudhary C.et.al.   19608861
Structure:
1E8O   1E8S   1RY1   4UYJ   4UYK   5AOX     

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	MPQYQTWEEF SRAAEKLYLA DPMKARVVLK YRHSDGNLCV KVTDDLVCLV YKTDQAQDVK 
61:	KIEKFHSQLM RLMVAKEARN VTMETE