Structural highlights
Function
[SRP54_BACSU] Involved in targeting and insertion of nascent membrane proteins into the cytoplasmic membrane. Binds to the hydrophobic signal sequence of the ribosome-nascent chain (RNC) as it emerges from the ribosomes. The SRP-RNC complex is then targeted to the cytoplasmic membrane where it interacts with the SRP receptor FtsY. Interaction with FtsY leads to the transfer of the RNC complex to the Sec translocase for insertion into the membrane, the hydrolysis of GTP by both Ffh and FtsY, and the dissociation of the SRP-FtsY complex into the individual components (Probable).[1]
Publication Abstract from PubMed
The signal recognition particle (SRP) recognizes signal sequences of nascent polypeptides and targets ribosome-nascent chain complexes to membrane translocation sites. In eukaryotes, translating ribosomes are slowed down by the Alu domain of SRP to allow efficient targeting. In prokaryotes, however, little is known about the structure and function of Alu domain-containing SRPs. Here, we report a complete molecular model of SRP from the Gram-positive bacterium Bacillus subtilis, based on cryo-EM. The SRP comprises two subunits, 6S RNA and SRP54 or Ffh, and it facilitates elongation slowdown similarly to its eukaryotic counterpart. However, protein contacts with the small ribosomal subunit observed for the mammalian Alu domain are substituted in bacteria by RNA-RNA interactions of 6S RNA with the alpha-sarcin-ricin loop and helices H43 and H44 of 23S rRNA. Our findings provide a structural basis for cotranslational targeting and RNA-driven elongation arrest in prokaryotes.
Translational arrest by a prokaryotic signal recognition particle is mediated by RNA interactions.,Beckert B, Kedrov A, Sohmen D, Kempf G, Wild K, Sinning I, Stahlberg H, Wilson DN, Beckmann R Nat Struct Mol Biol. 2015 Sep 7. doi: 10.1038/nsmb.3086. PMID:26344568[2]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Nakamura K, Nishiguchi M, Honda K, Yamane K. The Bacillus subtilis SRP54 homologue, Ffh, has an intrinsic GTPase activity and forms a ribonucleoprotein complex with small cytoplasmic RNA in vivo. Biochem Biophys Res Commun. 1994 Mar 30;199(3):1394-9. PMID:7511896 doi:http://dx.doi.org/10.1006/bbrc.1994.1385
- ↑ Beckert B, Kedrov A, Sohmen D, Kempf G, Wild K, Sinning I, Stahlberg H, Wilson DN, Beckmann R. Translational arrest by a prokaryotic signal recognition particle is mediated by RNA interactions. Nat Struct Mol Biol. 2015 Sep 7. doi: 10.1038/nsmb.3086. PMID:26344568 doi:http://dx.doi.org/10.1038/nsmb.3086
