Related Experiment Video

Updated: Jul 26, 2026

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

8.1K

A mitofusin-dependent docking ring complex triggers mitochondrial fusion in vitro

Tobias Brandt1, Laetitia Cavellini2, Werner Kühlbrandt1

  • 1Max Planck Institute of Biophysics, Frankfurt, Germany.

Elife
|June 3, 2016
PubMed

Insights

Mitochondrial outer membrane fusion, essential for organelle function, is mediated by mitofusins. This study visualizes the fusion process, revealing a docking ring complex that forms and triggers membrane merging during GTP hydrolysis.

Area of Science:

  • Cell Biology
  • Mitochondrial Dynamics
  • Membrane Biology

Background:

  • Mitochondrial outer membrane fusion is vital for cellular health and function.
  • Mitofusins, large GTPases, are key regulators of this process.
  • The precise mechanistic steps of mitochondrial attachment and fusion remain unclear.

Purpose of the Study:

  • To elucidate the discrete steps involved in mitochondrial outer membrane fusion.
  • To visualize the molecular complexes mediating mitochondrial attachment and fusion in vitro.
  • To understand the role of GTP hydrolysis in driving the fusion process.

Main Methods:

  • Utilized an in vitro mitochondrial fusion assay.
  • Employed electron cryo-tomography (cryo-ET) to visualize mitochondrial junctions.
  • Isolated mitochondria from Saccharomyces cerevisiae for analysis.

Main Results:

  • Observed novel complexes mediating mitochondrial attachment.
  • Demonstrated that GTP hydrolysis cycles progressively form a docking ring structure at extended contact sites.
  • Showed that further GTP hydrolysis initiates local outer membrane fusion at the contact periphery.

Conclusions:

  • Unraveled key mechanistic features of mitofusin-dependent outer membrane fusion.
  • Provided a high-resolution visualization of mitochondrial fusion intermediates.
  • Advanced the understanding of how mitochondria connect and merge, crucial for organelle homeostasis.
Keywords:
S. cerevisiaebiophysicscell biologycryo-EMdynamin-related-proteinsmembrane fusionmitochondriamitochondrial dynamicsmitofusinstructural biology

More Related Videos

Author Spotlight: Oxygen-Independent Assays to Measure Mitochondrial Function in Mammals05:59

Author Spotlight: Oxygen-Independent Assays to Measure Mitochondrial Function in Mammals

Published on: May 19, 2023

3.6K
Quantitative Analysis of Mitochondria-Associated Endoplasmic Reticulum Membrane (MAM) Stabilization in a Neural Model of Alzheimer's Disease (AD)06:41

Quantitative Analysis of Mitochondria-Associated Endoplasmic Reticulum Membrane (MAM) Stabilization in a Neural Model of Alzheimer's Disease (AD)

Published on: January 10, 2025

1.3K

Related Concept Videos

Mitochondrial Membranes01:45

Mitochondrial Membranes

A single mitochondrion is a bean-shaped organelle enclosed by a double-membrane system. The outer membrane of mitochondria is smooth and contains many porins - the integral membrane transporters. Porins enable free diffusion of ions and small uncharged molecules through the outer mitochondrial membrane but limit the transport of molecules larger than 5000 Daltons. Further, the outer mitochondrial membrane forms a unique structure called membrane contact sites with other subcellular organelles,...
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...
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...
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,...
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...
SNAREs and Membrane Fusion01:43

SNAREs and Membrane Fusion

Once a transport vesicle has recognized its target organelle, the vesicular membrane needs to fuse with the target membrane to unload the cargo. Transmembrane proteins called SNAREs present on organelle membranes and their vesicles, mediate vesicle fusion.
SNAREs exist in pairs that symmetrically interact and catalyze the fusion of the lipid bilayers in vesicle and target organelle. v-SNARE in the vesicle membrane are single polypeptide chains that bind to a complementary t-SNARE, composed of 2...