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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:Q9UGP8
Protein Name:Translocation protein Sec63 homolog
Length:760
Molecular Weight:87997.00
Species:Homo sapiens (Human) [9606]
Number of TMSs:3
Location1 / Topology2 / Orientation3: Endoplasmic reticulum membrane1 / Multi-pass membrane protein2
Substrate protein polypeptide chain

Cross database links:

RefSeq: NP_009145.1   
Entrez Gene ID: 11231   
Pfam: PF00226    PF02889   
OMIM: 174050  phenotype
608648  gene
KEGG: hsa:11231   

Gene Ontology

GO:0005789 C:endoplasmic reticulum membrane
GO:0016021 C:integral to membrane
GO:0031072 F:heat shock protein binding
GO:0004872 F:receptor activity
GO:0051082 F:unfolded protein binding
GO:0006457 P:protein folding
GO:0006612 P:protein targeting to membrane

References (7)

[1] “Molecular characterization of a novel mammalian DnaJ-like Sec63p homolog.”  Skowronek M.H.et.al.   10543453
[2] “Mammalian Sec61 is associated with Sec62 and Sec63.”  Meyer H.-A.et.al.   10799540
[3] “The DNA sequence and analysis of human chromosome 6.”  Mungall A.J.et.al.   14574404
[4] “The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).”  The MGC Project Teamet.al.   15489334
[5] “The full-ORF clone resource of the German cDNA consortium.”  Bechtel S.et.al.   17974005
[6] “Mutations in SEC63 cause autosomal dominant polycystic liver disease.”  Davila S.et.al.   15133510
[7] “A quantitative atlas of mitotic phosphorylation.”  Dephoure N.et.al.   18669648

External Searches:

Analyze:

Predict TMSs (Predict number of transmembrane segments)
Window Size: Angle:  
FASTA formatted sequence
1:	MAGQQFQYDD SGNTFFYFLT SFVGLIVIPA TYYLWPRDQN AEQIRLKNIR KVYGRCMWYR 
61:	LRLLKPQPNI IPTVKKIVLL AGWALFLFLA YKVSKTDREY QEYNPYEVLN LDPGATVAEI 
121:	KKQYRLLSLK YHPDKGGDEV MFMRIAKAYA ALTDEESRKN WEEFGNPDGP QATSFGIALP 
181:	AWIVDQKNSI LVLLVYGLAF MVILPVVVGS WWYRSIRYSG DQILIRTTQI YTYFVYKTRN 
241:	MDMKRLIMVL AGASEFDPQY NKDATSRPTD NILIPQLIRE IGSINLKKNE PPLTCPYSLK 
301:	ARVLLLSHLA RMKIPETLEE DQQFMLKKCP ALLQEMVNVI CQLIVMARNR EEREFRAPTL 
361:	ASLENCMKLS QMAVQGLQQF KSPLLQLPHI EEDNLRRVSN HKKYKIKTIQ DLVSLKESDR 
421:	HTLLHFLEDE KYEEVMAVLG SFPYVTMDIK SQVLDDEDSN NITVGSLVTV LVKLTRQTMA 
481:	EVFEKEQSIC AAEEQPAEDG QGETNKNRTK GGWQQKSKGP KKTAKSKKKK PLKKKPTPVL 
541:	LPQSKQQKQK QANGVVGNEA AVKEDEEEVS DKGSDSEEEE TNRDSQSEKD DGSDRDSDRE 
601:	QDEKQNKDDE AEWQELQQSI QRKERALLET KSKITHPVYS LYFPEEKQEW WWLYIADRKE 
661:	QTLISMPYHV CTLKDTEEVE LKFPAPGKPG NYQYTVFLRS DSYMGLDQIK PLKLEVHEAK 
721:	PVPENHPQWD TAIEGDEDQE DSEGFEDSFE EEEEEEEDDD