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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:P09132
Protein Name:Signal recognition particle 19 kDa protein aka SRP19
Length:144
Molecular Weight:16156.00
Species:Homo sapiens (Human) [9606]
Location1 / Topology2 / Orientation3: Cytoplasm1
Substrate protein polypeptide chain

Cross database links:

RefSeq: NP_003126.1   
Entrez Gene ID: 6728   
Pfam: PF01922   
OMIM: 182175  gene
KEGG: hsa:6728   

Gene Ontology

GO:0005730 C:nucleolus
GO:0005786 C:signal recognition particle, endoplasmic re...
GO:0008312 F:7S RNA binding
GO:0042493 P:response to drug
GO:0006614 P:SRP-dependent cotranslational protein targe...

References (5)

[1] “Isolation and characterization of a cDNA clone encoding the 19 kDa protein of signal recognition particle (SRP): expression and binding to 7SL RNA.”  Lingelbach K.et.al.   2460823
[2] “Complete sequencing and characterization of 21,243 full-length human cDNAs.”  Ota T.et.al.   14702039
[3] “The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).”  The MGC Project Teamet.al.   15489334
[4] “Lys-N and trypsin cover complementary parts of the phosphoproteome in a refined SCX-based approach.”  Gauci S.et.al.   19413330
[5] “Crystal structure of an early protein-RNA assembly complex of the signal recognition particle.”  Wild K.et.al.   11641499
Structure:
1JID   1MFQ   1RY1   2J37   3KTV   4P3E   5M73     

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	MACAAARSPA DQDRFICIYP AYLNNKKTIA EGRRIPISKA VENPTATEIQ DVCSAVGLNV 
61:	FLEKNKMYSR EWNRDVQYRG RVRVQLKQED GSLCLVQFPS RKSVMLYAAE MIPKLKTRTQ 
121:	KTGGADQSLQ QGEGSKKGKG KKKK