7syl
From Proteopedia
Structure of the HCV IRES bound to the 40S ribosomal subunit, closed conformation. Structure 6(delta dII)
Structural highlights
FunctionRSSA_RABIT Required for the assembly and/or stability of the 40S ribosomal subunit (PubMed:23873042, PubMed:25601755). Required for the processing of the 20S rRNA-precursor to mature 18S rRNA in a late step of the maturation of 40S ribosomal subunits (PubMed:23873042, PubMed:25601755). Also functions as a cell surface receptor for laminin (By similarity). Plays a role in cell adhesion to the basement membrane and in the consequent activation of signaling transduction pathways (By similarity). May play a role in cell fate determination and tissue morphogenesis (By similarity). Also acts as a receptor for several other ligands, including the pathogenic prion protein, viruses, and bacteria. Acts as a PPP1R16B-dependent substrate of PPP1CA (By similarity).[HAMAP-Rule:MF_03016][1] [2] Publication Abstract from PubMedHepatitis C virus mRNA contains an internal ribosome entry site (IRES) that mediates end-independent translation initiation, requiring a subset of eukaryotic initiation factors (eIFs). Biochemical studies revealed that direct binding of the IRES to the 40S ribosomal subunit places the initiation codon into the P site, where it base pairs with eIF2-bound Met-tRNAiMet forming a 48S initiation complex. Subsequently, eIF5 and eIF5B mediate subunit joining, yielding an elongation-competent 80S ribosome. Initiation can also proceed without eIF2, in which case Met-tRNAiMet is recruited directly by eIF5B. However, the structures of initiation complexes assembled on the HCV IRES, the transitions between different states, and the accompanying conformational changes have remained unknown. To fill these gaps, we now obtained cryo-EM structures of IRES initiation complexes, at resolutions up to 3.5 A, that cover all major stages from the initial ribosomal association, through eIF2-containing 48S initiation complexes, to eIF5B-containing complexes immediately prior to subunit joining. These structures provide insights into the dynamic network of 40S/IRES contacts, highlight the role of IRES domain II, and reveal conformational changes that occur during the transition from eIF2- to eIF5B-containing 48S complexes and prepare them for subunit joining. Molecular architecture of 40S translation initiation complexes on the hepatitis C virus IRES.,Brown ZP, Abaeva IS, De S, Hellen CUT, Pestova TV, Frank J EMBO J. 2022 Aug 16;41(16):e110581. doi: 10.15252/embj.2022110581. Epub 2022 Jul , 13. PMID:35822879[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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