Signal recognition particle protein

Signal recognition particle (SRP) is a ribonucleoprotein which targets specific proteins to the endoplasmic reticulum (ER) in eukaryotes and the plasma membrane in prokaryotes. In eukaryotes SRP binds to the signal sequence of a newly synthesized polypeptide as it emerges from the ribosome. The binding allows for the coupling of the translation process to the translocation process. The SRP targets the nascent protein to the ER by docking into the SRP receptor. The eukaryotic SRP which has GTPase activity, is composed of SRP9, SRP14, SRP19, SRP54, SRP68, SRP72 and 7S RNA. The prokaryotic SRP is composed of FFH (SRP54-like) and 4.5S RNA.

3D structures of SRP3D structures of SRP

1914 – SRP9/SRP14 – mouse
1ls1, 2j45, 2j46, 1ffh, 1ng1, 3ng1 - TaSRP54-like NG domain – Thermus aquaticus
2ng1 - TaSRP54-like NG domain (mutant)
2ffh - TaSRP54-like residues 1-425 (mutant)
1kvn, 1kvv – SRP19 (mutant) – Archaeoglobus fulgidus – NMR
1qb2 – hSRP54
2hug – AtSRP43 chromo-2 domain + SRP54 M domain – Arabidopsis thaliana – NMR
3deo - AtSRP43 residues 85-267
3ui2 - AtSRP43 residues 84-327 + AtSRP54 RRKR motif
3dlu, 3dlv – SRP19 – Pyrococcus furiosus
2w9j – SRP14 residues 1-91 – fission yeast

SRP complexes with RNA

1e8o, 1e8s - hSRP9 + hSRP14 + 7S RNA – human
1ry1 - hSRP9 + hSRP14 + hSRP19 + hSRP54 + 7S RNA
1jid – hSRP19 + RNA
3ktv - hSRP19 + RNA S domain
3ktw - SRP19 + RNA S domain – Sulfolobus solfataricus
1lng – MjSRP19 + RNA – Methanocaldococcus jannaschii
1l9a - MjSRP19 (mutant) + RNA
2v3c, 3ndb - MjSRP19 + MjSRP54 + 7S RNA
1mfq – hSRP19 + hSRP54 M domain + 7S RNA S domain
2iy3 – TaSRP54-like + RNA - EM
1dul, 1hq1 – EcSRP54-like C terminal + RNA – Escherichia coli
3lqx - EcSRP54-like + RNA + Co-hexamine
2xkv - EcSRP54-like NG+M domains + 4.5SRNA – EM
2xxa - EcSRP54-like residues 1-433 (mutant) + cell division protein FTSY residues 196-497+ 4.5SRNA
2pxb, 2pxd, 2pxe, 2pxf, 2pxk, 2pxl, 2pxq, 2pxq, 2pxt, 2pxu, 2pxv - EcSRP54-like C terminal + 4.5SRNA domain IV (mutant)
2go5 – dSRP19 + SRP54 + hSRP receptor α subunit + mSRP receptor b subunit + ribosomal proteins L23, L31, L35 + RNA – dog
2j28 – EcSRP54-like + 70S ribosome – EM
2j37 - hSRP19 + dSRP54 + ribosomal proteins L23, L31, L35 + RNA – wheat – EM

Other SRP complexes

1jpj, 1jpn, 2c04 – TaSRP54-like NG domain + GMPPNP
1o87, 2c03 - TaSRP54-like NG domain + GDP
1okk, 1rj9, 2cnw - TaSRP54-like NG domain + cell division protein FTSY
2j7p - TaSRP54-like NG domain + cell division protein FTSY + GMPPNP
3dep - AtSRP43 residues 85-267 + polypeptide