Related Experiment Video

Updated: Oct 1, 2025

A Model Membrane Platform for Reconstituting Mitochondrial Membrane Dynamics
10:31

A Model Membrane Platform for Reconstituting Mitochondrial Membrane Dynamics

Published on: September 2, 2020

7.7K

The multi-factor modulated biogenesis of the mitochondrial multi-span protein Om14

Jialin Zhou1, Martin Jung2, Kai S Dimmer1

  • 1Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany.

The Journal of Cell Biology
|March 9, 2022
PubMed

Insights

Mitochondrial outer membrane protein biogenesis is complex. Researchers found that while full-length Om14 ensures accurate mitochondrial targeting, its integration depends on protein unfolding, hydrophobicity, and membrane fluidity, not solely on specific proteins.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The mitochondrial outer membrane (MOM) contains multi-span proteins crucial for cellular functions.
  • Understanding the biogenesis of these complex transmembrane proteins is essential for cellular health.

Purpose of the Study:

  • To investigate the biogenesis pathway of multi-span proteins in the mitochondrial outer membrane.
  • To identify factors influencing the targeting specificity and membrane integration of Om14, a model multi-span protein.

Main Methods:

  • Utilized yeast mitochondria and truncation variants of the Om14 protein.
  • Employed a specific insertion assay and deletion strains to analyze protein targeting and integration.
  • Assessed the impact of protein unfolding, hydrophobicity, and membrane fluidity on import capacity.

Main Results:

  • Full-length Om14 exhibits precise mitochondrial targeting specificity; truncated variants show compromised fidelity.
  • Cytosolic exposure of proteins does not significantly contribute to the biogenesis process.
  • Mim1 and Porin facilitate Om14 membrane integration but are not essential; unfolding, hydrophobicity, and membrane fluidity enhance import.

Conclusions:

  • Mitochondrial outer membrane multi-span protein biogenesis involves diverse pathways.
  • Both proteinaceous factors and membrane properties play variable roles in the efficiency of Om14 import and integration.

More Related Videos

Author Spotlight: Unveiling Mitochondrial Contact Sites and Architectural Insights07:55

Author Spotlight: Unveiling Mitochondrial Contact Sites and Architectural Insights

Published on: June 16, 2023

1.6K
Rapid Isolation of the Mitoribosome from HEK Cells09:33

Rapid Isolation of the Mitoribosome from HEK Cells

Published on: October 4, 2018

11.3K

Related Concept Videos

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...
3.4K
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...
3.3K
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...
4.5K
Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
5.8K
Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70  chaperones are targetted to TOM20-TOM22 receptor complexes.
Most of the mitochondrial...
2.7K
Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

Nuclear encoded mitochondrial precursors are imported to the inner membrane in a multistep process involving two separate translocons, TIM22 and TIM23. TIM23 is a cation-selective pore that remains closed by the N terminal segment of the protein. Negative charges on the TIM23 act as a receptor for the incoming precursor, pulling the positively charged matrix-targeting sequence for peptide insertion and translocation.
Transport of mitochondrial precursors across the TIM23 channel is driven by...
4.1K