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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:Q9UHB9
Protein Name:Signal recognition particle 68 kDa protein aka SRP68
Length:627
Molecular Weight:70730.00
Species:Homo sapiens (Human) [9606]
Number of TMSs:1
Location1 / Topology2 / Orientation3: Cytoplasm1
Substrate protein polypeptide chain

Cross database links:

RefSeq: NP_055045.2   
Entrez Gene ID: 6730   
OMIM: 604858  gene
KEGG: hsa:6730   

Gene Ontology

GO:0005783 C:endoplasmic reticulum
GO:0005730 C:nucleolus
GO:0005840 C:ribosome
GO:0005786 C:signal recognition particle, endoplasmic re...
GO:0003723 F:RNA binding
GO:0005047 F:signal recognition particle binding
GO:0042493 P:response to drug

References (8)

[1] “Signal recognition particle components in the nucleolus.”  Politz J.C.et.al.   10618370
[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] “Global survey of phosphotyrosine signaling identifies oncogenic kinases in lung cancer.”  Rikova K.et.al.   18083107
[5] “Phosphoproteome of resting human platelets.”  Zahedi R.P.et.al.   18088087
[6] “Kinase-selective enrichment enables quantitative phosphoproteomics of the kinome across the cell cycle.”  Daub H.et.al.   18691976
[7] “A quantitative atlas of mitotic phosphorylation.”  Dephoure N.et.al.   18669648
[8] “Lysine acetylation targets protein complexes and co-regulates major cellular functions.”  Choudhary C.et.al.   19608861
Structure:
4P3E   4P3F   5M72   5M73   5WRV     

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	MAAEKQVPGG GGGGGSGGGG GSGGGGSGGG RGAGGEENKE NERPSAGSKA NKEFGDSLSL 
61:	EILQIIKESQ QQHGLRHGDF QRYRGYCSRR QRRLRKTLNF KMGNRHKFTG KKVTEELLTD 
121:	NRYLLLVLMD AERAWSYAMQ LKQEANTEPR KRFHLLSRLR KAVKHAEELE RLCESNRVDA 
181:	KTKLEAQAYT AYLSGMLRFE HQEWKAAIEA FNKCKTIYEK LASAFTEEQA VLYNQRVEEI 
241:	SPNIRYCAYN IGDQSAINEL MQMRLRSGGT EGLLAEKLEA LITQTRAKQA ATMSEVEWRG 
301:	RTVPVKIDKV RIFLLGLADN EAAIVQAESE ETKERLFESM LSECRDAIQV VREELKPDQK 
361:	QRDYILEGEP GKVSNLQYLH SYLTYIKLST AIKRNENMAK GLQRALLQQQ PEDDSKRSPR 
421:	PQDLIRLYDI ILQNLVELLQ LPGLEEDKAF QKEIGLKTLV FKAYRCFFIA QSYVLVKKWS 
481:	EALVLYDRVL KYANEVNSDA GAFKNSLKDL PDVQELITQV RSEKCSLQAA AILDANDAHQ 
541:	TETSSSQVKD NKPLVERFET FCLDPSLVTK QANLVHFPPG FQPIPCKPLF FDLALNHVAF 
601:	PPLEDKLEQK TKSGLTGYIK GIFGFRS