9H55

Assembly intermediate of human mitochondrial ribosome small subunit in complex with NOA1 and TFB1M (state N3)

This is a non-PDB format compatible entry.

Summary for 9H55

• Entry DOI: 10.2210/pdb9h55/pdb
• EMDB information: 51877
• Descriptor: 12S mitochondrial rRNA, 28S ribosomal protein S12, mitochondrial, 28S ribosomal protein S14, mitochondrial, ... (38 entities in total)
• Functional Keywords: mitochondria, small subunit, assembly, noa1, ribosome
• Biological source: Homo sapiens (human); More
• Total number of polymer chains: 32
• Total formula weight: 1265526.34

Authors

Singh, V.,Shiriaev, D.,Khawaja, A.,Rorbach, J. (deposition date: 2024-10-22, release date: 2026-05-13, Last modification date: 2026-07-08)

Primary citation

Singh, V.,Shiriaev, D.,Bilalli, L.,Khawaja, A.,Rorbach, J.
Pseudouridine synthase PUS1 and initiation factor mtIF2 are human mitoribosomal small subunit assembly factors.
Nat Commun, 17:-, 2026

PubMed Abstract: Assembly of the mitochondrial ribosome (mitoribosome) is a crucial step in mitochondrial gene expression. This process facilitates mitochondrial translation, which produces essential subunits of the oxidative phosphorylation machinery-the cell's primary energy-producing machinery. Disruptions in mitoribosome assembly can lead to severe human diseases. Given its fundamental importance, detailed structural analysis of mitoribosome assembly pathways is essential for advancing our understanding of mitochondrial function in both health and disease. In this study, we characterize twelve distinct assembly states of the mitoribosomal small subunit (mtSSU) isolated from human cells. Our findings reveal the intricate details of the final maturation stages of the mtSSU platform, decoding center, and the 3'-end of 12S rRNA. This process is governed by coordinated actions of assembly factors that ensure precise, stepwise rRNA folding and the integration of mitoribosomal proteins into the developing subunit. Our approach identifies pseudouridine synthase PUS1 and initiation factor mtIF2 as assembly factors, expanding their known roles beyond mt-tRNA maturation and translation, respectively. In addition, the identified assembly intermediates provide insight into the modular nature of mtSSU biogenesis in mitochondria and further link late-stage assembly to the acquisition of translational competence.

PubMed: 42342677
DOI: 10.1038/s41467-026-74700-x

Experimental method

ELECTRON MICROSCOPY (3.4 Å)