9PR4

In Situ Structure of the Human Mitochondrial Large Subunit 39S in Complex with TACO1

This is a non-PDB format compatible entry.

Summary for 9PR4

• Entry DOI: 10.2210/pdb9pr4/pdb
• EMDB information: 71797
• Descriptor: 39S ribosomal protein L32, mitochondrial, 39S ribosomal protein L41, mitochondrial, Translational activator of cytochrome c oxidase 1, ... (64 entities in total)
• Functional Keywords: mitochondria, mitoribosome, inner membrane, ribosome
• Biological source: Homo sapiens (human); More
• Total number of polymer chains: 63
• Total formula weight: 2017651.33

Authors

Wang, S.,Xiong, Y.,Zhang, Y. (deposition date: 2025-07-23, release date: 2026-02-18)

Primary citation

Wang, S.,Brischigliaro, M.,Zhang, Y.,Wu, C.,Zheng, W.,Barrientos, A.,Xiong, Y.
Structural basis of TACO1-mediated efficient mitochondrial translation.
Nat Commun, 2026

PubMed Abstract: Translation elongation is a universally conserved step in protein synthesis, relying on elongation factors that engage the ribosomal L7/L12 stalk to mediate aminoacyl-tRNA delivery, accommodation, and ribosomal translocation. Using in organello cryo-electron microscopy, we reveal how the mitochondrial translation accelerator TACO1 promotes efficient elongation on human mitoribosomes. TACO1 binds the mitoribosomal region typically bound by elongation factor Tu (mtEF-Tu), bridging the large and small subunits via contacts with 16S rRNA, bL12m, A-site tRNA, and uS12m. While active throughout elongation, TACO1 is especially critical when translating polyproline motifs. Its absence prolongs mtEF-Tu residence in A/T states, causes persistent mitoribosomal stalling and premature subunit dissociation. Structural analyses indicate that TACO1 competes with mtEF-Tu for mitoribosome binding, stabilizes A-site tRNA, and enhances peptidyl transfer through a mechanism distinct from EF-P and eIF5A. These findings suggest that bacterial TACO1 orthologs may serve analogous roles, highlighting an evolutionarily conserved strategy for maintaining elongation efficiency during challenging translation events.

PubMed: 41663403
DOI: 10.1038/s41467-026-69156-y

Experimental method

ELECTRON MICROSCOPY (2.77 Å)