5uq8 | pdb_00005uq8
70S ribosome complex with dnaX mRNA stem-loop and E-site tRNA ("out" conformation)
Structural highlights
FunctionRL3_THET8 One of the primary rRNA binding proteins, it binds directly near the 3'-end of the 23S rRNA, where it nucleates assembly of the 50S subunit (By similarity).[HAMAP-Rule:MF_01325_B] Publication Abstract from PubMedStructured mRNAs positioned downstream of the ribosomal decoding center alter gene expression by slowing protein synthesis. Here, we solved the cryo-EM structure of the bacterial ribosome bound to an mRNA containing a 3' stem loop that regulates translation. Unexpectedly, the E-site tRNA adopts two distinct orientations. In the first structure, normal interactions with the 50S and 30S E site are observed. However, in the second structure, although the E-site tRNA makes normal interactions with the 50S E site, its anticodon stem loop moves approximately 54 A away from the 30S E site to interact with the 30S head domain and 50S uL5. This position of the E-site tRNA causes the uL1 stalk to adopt a more open conformation that likely represents an intermediate state during E-site tRNA dissociation. These results suggest that structured mRNAs at the entrance channel restrict 30S subunit movement required during translation to slow E-site tRNA dissociation. Alternative Mode of E-Site tRNA Binding in the Presence of a Downstream mRNA Stem Loop at the Entrance Channel.,Zhang Y, Hong S, Ruangprasert A, Skiniotis G, Dunham CM Structure. 2018 Mar 6;26(3):437-445.e3. doi: 10.1016/j.str.2018.01.013. Epub 2018, Feb 15. PMID:29456023[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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