5lzc

Structure of SelB-Sec-tRNASec bound to the 70S ribosome in the codon reading state (CR)

Loading... Status: waiting for Mol* initialization Structural highlights 5lzc is a 10 chain structure with sequence from Escherichia coli. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Electron Microscopy, Resolution 4.8Å Ligands: 1MG, 2MA, 2MG, 3TD, 4OC, 4SU, 5MC, 5MU, 6IA, 6MZ, FME, G7M, GNP, H2U, MA6, MG, OMC, OMG, OMU, PSU, SEC, UR3, ZN Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function RS4_ECOLI One of two assembly initiator proteins for the 30S subunit, it binds directly to 16S rRNA where it nucleates assembly of the body of the 30S subunit. With S5 and S12 plays an important role in translational accuracy; many suppressors of streptomycin-dependent mutants of protein S12 are found in this protein, some but not all of which decrease translational accuracy (ram, ribosomal ambiguity mutations). Plays a role in mRNA unwinding by the ribosome, possibly by forming part of a processivity clamp. Protein S4 is also a translational repressor protein, it controls the translation of the alpha-operon (which codes for S13, S11, S4, RNA polymerase alpha subunit, and L17) by binding to its mRNA. Also functions as a rho-dependent antiterminator of rRNA transcription, increasing the synthesis of rRNA under conditions of excess protein, allowing a more rapid return to homeostasis. Binds directly to RNA polymerase. Publication Abstract from PubMed In all domains of life, selenocysteine (Sec) is delivered to the ribosome by selenocysteine-specific tRNA (tRNASec) with the help of a specialized translation factor, SelB in bacteria. Sec-tRNASec recodes a UGA stop codon next to a downstream mRNA stem-loop. Here we present the structures of six intermediates on the pathway of UGA recoding in Escherichia coli by single-particle cryo-electron microscopy. The structures explain the specificity of Sec-tRNASec binding by SelB and show large-scale rearrangements of Sec-tRNASec. Upon initial binding of SelB-Sec-tRNASec to the ribosome and codon reading, the 30S subunit adopts an open conformation with Sec-tRNASec covering the sarcin-ricin loop (SRL) on the 50S subunit. Subsequent codon recognition results in a local closure of the decoding site, which moves Sec-tRNASec away from the SRL and triggers a global closure of the 30S subunit shoulder domain. As a consequence, SelB docks on the SRL, activating the GTPase of SelB. These results reveal how codon recognition triggers GTPase activation in translational GTPases. The pathway to GTPase activation of elongation factor SelB on the ribosome.,Fischer N, Neumann P, Bock LV, Maracci C, Wang Z, Paleskava A, Konevega AL, Schroder GF, Grubmuller H, Ficner R, Rodnina MV, Stark H Nature. 2016 Dec 1;540(7631):80-85. doi: 10.1038/nature20560. Epub 2016 Nov 14. PMID:27842381 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Elongation factor 3D structures Ribosome 3D structures

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