3jan

Structure of the scanning state of the mammalian SRP-ribosome complexStructure of the scanning state of the mammalian SRP-ribosome complex

3jan, resolution 3.75Å Show:Asymmetric Unit Biological Assembly Structural highlights 3jan is a 10 chain structure with sequence from Oryctolagus cuniculus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Electron Microscopy, Resolution 3.75Å Ligands: Experimental data: Check Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed The universally conserved signal recognition particle (SRP) is essential for the biogenesis of most integral membrane proteins. SRP scans the nascent chains of translating ribosomes, preferentially engaging those with hydrophobic targeting signals, and delivers these ribosome-nascent chain complexes to the membrane. Here, we present structures of native mammalian SRP-ribosome complexes in the scanning and engaged states. These structures reveal the near-identical SRP architecture of these two states, show many of the SRP-ribosome interactions at atomic resolution, and suggest how the polypeptide-binding M domain selectively engages hydrophobic signals. The scanning M domain, pre-positioned at the ribosomal exit tunnel, is auto-inhibited by a C-terminal amphipathic helix occluding its hydrophobic binding groove. Upon engagement, the hydrophobic targeting signal displaces this amphipathic helix, which then acts as a protective lid over the signal. Biochemical experiments suggest how scanning and engagement are coordinated with translation elongation to minimize exposure of hydrophobic signals during membrane targeting. Structures of the scanning and engaged states of the mammalian SRP-ribosome complex.,Voorhees RM, Hegde RS Elife. 2015 Jul 9;4. doi: 10.7554/eLife.07975. PMID:26158507 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Ribosome 3D structures Signal recognition particle receptor 3D structures Transfer RNA (tRNA)