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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:Q9UHQ4
Protein Name:B-cell receptor-associated protein 29
Length:241
Molecular Weight:28320.00
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:

Entrez Gene ID: 55973   
Pfam: PF05529   

Gene Ontology

GO:0005789 C:endoplasmic reticulum membrane
GO:0016021 C:integral to membrane
GO:0006915 P:apoptosis
GO:0006886 P:intracellular protein transport
GO:0016192 P:vesicle-mediated transport

References (3)

[1] “Gene expression profiling in the human hypothalamus-pituitary-adrenal axis and full-length cDNA cloning.”  Hu R.-M.et.al.   10931946
[2] “The DNA sequence of human chromosome 7.”  Hillier L.W.et.al.   12853948
[3] “The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).”  The MGC Project Teamet.al.   15489334
Structure:
4W7Y   4W7Z   4W80     

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	MTLQWAAVAT FLYAEIGLIL IFCLPFIPPQ RWQKIFSFNV WGKIATFWNK AFLTIIILLI 
61:	VLFLDAVREV RKYSSVHTIE KSSTSRPDAY EHTQMKLFRS QRNLYISGFS LFFWLVLRRL 
121:	VTLITQLAKE LSNKGVLKTQ AENTNKAAKK FMEENEKLKR ILKSHGKDEE CVLEAENKKL 
181:	VEDQEKLKTE LRKTSDALSK AQNDVMEMKM QSERLSKEYD QLLKEHSELQ DRLERGNKKR 
241:	L