ジャーナル: Nat Struct Mol Biol / 年: 2026 タイトル: Translational activators align mRNAs at the small mitoribosomal subunit for translation initiation. 著者: Joseph B Bridgers / Andreas Carlström / Dawafuti Sherpa / Mary T Couvillion / Urška Rovšnik / Jingjing Gao / Bowen Wan / Sichen Shao / Martin Ott / L Stirling Churchman / 要旨: Mitochondrial gene expression is essential for oxidative phosphorylation. Mitochondrial-encoded mRNAs are translated by dedicated mitochondrial ribosomes (mitoribosomes), whose regulation remains ...Mitochondrial gene expression is essential for oxidative phosphorylation. Mitochondrial-encoded mRNAs are translated by dedicated mitochondrial ribosomes (mitoribosomes), whose regulation remains elusive. In Saccharomyces cerevisiae, nuclear-encoded mitochondrial translational activators (TAs) facilitate transcript-specific translation by a yet unknown mechanism. Here, we investigated the function of TAs containing RNA-binding pentatricopeptide repeats using selective mitoribosome profiling and cryo-electron microscopy (cryo-EM) structural analysis. These analyses show that TAs exhibit strong selectivity for mitoribosomes initiating on their target transcripts. Moreover, TA-mitoribosome footprints indicate that TAs recruit mitoribosomes proximal to the start codon. Two cryo-EM structures of mRNA-TA complexes bound to mitoribosomes stalled in the post-initiation, pre-elongation state revealed the general mechanism of TA action. Specifically, the TAs bind to structural elements in the 5' untranslated region of the client mRNA and the mRNA channel exit to align the mRNA in the small subunit during initiation. Our findings provide a mechanistic basis for understanding how mitochondria achieve transcript-specific translation initiation without relying on general sequence elements to position mitoribosomes at start codons.
全体 : Mitoribosome in complex with translation activator complex (Aep1-...
全体
名称: Mitoribosome in complex with translation activator complex (Aep1-Aep2-Atp25C)
要素
複合体: Mitoribosome in complex with translation activator complex (Aep1-Aep2-Atp25C)
-
超分子 #1: Mitoribosome in complex with translation activator complex (Aep1-...
超分子
名称: Mitoribosome in complex with translation activator complex (Aep1-Aep2-Atp25C) タイプ: complex / ID: 1 / 親要素: 0 詳細: Small ribosomal subunit of the mitoribosome in complex with translation activator complex (Aep1-Aep2-Atp25C)
由来(天然)
生物種: Saccharomyces cerevisiae (パン酵母)
-
実験情報
-
構造解析
手法
クライオ電子顕微鏡法
解析
単粒子再構成法
試料の集合状態
particle
-
試料調製
緩衝液
pH: 7.5
凍結
凍結剤: ETHANE
-
電子顕微鏡法
顕微鏡
TFS KRIOS
撮影
フィルム・検出器のモデル: FEI FALCON IV (4k x 4k) 平均電子線量: 48.5 e/Å2