Related Experiment Video

Updated: Feb 23, 2026

Visualization of ATP Synthase Dimers in Mitochondria by Electron Cryo-tomography
10:39

Visualization of ATP Synthase Dimers in Mitochondria by Electron Cryo-tomography

Published on: September 14, 2014

31.1K

Structure of the Human Mitochondrial Ribosome Studied In Situ by Cryoelectron Tomography

Robert Englmeier1, Stefan Pfeffer2, Friedrich Förster3

  • 1Cryo-Electron Microscopy, Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, the Netherlands.

Structure (London, England : 1993)
|September 5, 2017
PubMed

Insights

Human mitoribosomes associate with the inner mitochondrial membrane via the mL45 protein. Unlike yeast, humans lack a second rRNA-mediated contact, leading to more variable membrane association for mitochondrial protein synthesis.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Structural Biology

Background:

  • Mitochondria possess their own genome and protein synthesis machinery, the mitochondrial ribosome (mitoribosome).
  • Mitoribosomes synthesize hydrophobic proteins crucial for the inner mitochondrial membrane.
  • The precise mechanism of mitoribosome membrane association was previously unclear.

Purpose of the Study:

  • To visualize and characterize the membrane association of human mitoribosomes.
  • To identify the specific proteins and structures involved in mitoribosome-inner mitochondrial membrane interactions.

Main Methods:

  • Cryoelectron tomography was employed to image human mitoribosomes within isolated mitochondria.
  • Subtomogram averaging was used to determine the structure of membrane-associated mitoribosomes.

Main Results:

  • A single primary contact site was identified between human mitoribosomes and the inner mitochondrial membrane.
  • This interaction is mediated by the mitochondria-specific protein mL45.
  • Human mitoribosomes lack a second rRNA-mediated contact site found in yeast, resulting in more variable membrane association.

Conclusions:

  • The mL45 protein is essential for anchoring human mitoribosomes to the inner mitochondrial membrane.
  • Differences in membrane association mechanisms between human and yeast mitoribosomes exist.
  • Despite structural variations, conserved elements facilitate mitoribosome alignment with membrane protein insertion machinery.
Keywords:
cryoelectron tomographymL45membrane insertionmitochondriamitochondrial membranemitoribosomephase plateribosomesubtomogram analysistranslation

More Related Videos

Rapid Isolation of the Mitoribosome from HEK Cells09:33

Rapid Isolation of the Mitoribosome from HEK Cells

Published on: October 4, 2018

11.8K
Visualization of Organelles In Situ by Cryo-STEM Tomography08:37

Visualization of Organelles In Situ by Cryo-STEM Tomography

Published on: June 23, 2023

3.2K

Related Concept Videos

Electron Microscope Tomography and Single-particle Reconstruction01:07

Electron Microscope Tomography and Single-particle Reconstruction

Transmission electron microscopy (TEM) can be used to determine the 3D structure of biological samples with the help of techniques such as electron microscope tomography and single-particle reconstruction. While single-particle reconstruction can examine macromolecules and macromolecular complexes in vitro conditions only, tomography permits the study of cell components or small cells in vivo.
Electron Tomography
Electron tomography can be performed either in TEM or STEM (scanning transmission...
3.0K
The Inner Mitochondrial Membrane01:28

The Inner Mitochondrial Membrane

The inner mitochondrial membrane is the primary site of ATP synthesis. The inner membrane domain that forms a smooth layer adjacent to the outer membrane is called the inner boundary membrane. This domain contains membrane transporters that drive metabolites in and out of the mitochondria.  In contrast, the inner membrane network that invaginates into the matrix space is called the cristae membrane. This domain accounts for principle mitochondrial function as it accommodates the protein...
4.8K
Porin Insertion in the Outer Mitochondrial Membrane01:12

Porin Insertion in the Outer Mitochondrial Membrane

Porins are beta-barrel proteins translocated to the mitochondrial outer membrane through the TOM complex into the intermembrane space. Porin precursors bind TIM chaperones within the intermembrane space and are guided to the Sorting and Assembly Machinery complex or SAM complex on the outer mitochondrial membrane.
Three models describe the assembly of porins by the SAM complex and their insertion into the outer membrane. Model 1 suggests that porins are assembled outside the SAM channel as the...
4.9K
Cryo-electron Microscopy01:28

Cryo-electron Microscopy

Conventional electron microscopy (EM) involves dehydration, fixation, and staining of biological samples, which distorts the native state of biological molecules and results in several artifacts. Also, the high-energy electron beam damages the sample and makes it difficult to obtain high-resolution images. These issues can be addressed using cryo-EM, which uses frozen samples and gentler electron beams. The technique was developed by Jacques Dubochet, Joachim Frank, and Richard Henderson, for...
4.4K
Structure of Porins01:21

Structure of Porins

Mitochondria, chloroplasts, and gram-negative bacteria have transmembrane, beta-barrel proteins called porins to mediate the free diffusion of ions and metabolites across the membrane. Mitochondrial porin precursors contain conserved amino acid sequences called beta signals at their C-terminal. Beta signals have a  motif of PoXGXXHyXHy (Po-Polar, X-Any amino acid, G-Glycine, Hy-LargeHydrophobic), which are crucial for precursor recognition to initiate precursor assembly. Beta-barrel...
4.0K
Mitochondrial Protein Sorting01:39

Mitochondrial Protein Sorting

Mitochondria are double-membrane organelles of the eukaryotes involved in cellular metabolism, signaling, ATP synthesis, and programmed cell death.  Each of these processes requires specific proteins and enzymes that must be correctly sorted to the right mitochondrial subcompartment for the proper functioning of the organelle.
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
5.8K