Jove
Visualize
Contact Us
JoVE
x logofacebook logolinkedin logoyoutube logo
ABOUT JoVE
OverviewLeadershipBlogJoVE Help Center
AUTHORS
Publishing ProcessEditorial BoardScope & PoliciesPeer ReviewFAQSubmit
LIBRARIANS
TestimonialsSubscriptionsAccessResourcesLibrary Advisory BoardFAQ
RESEARCH
JoVE JournalMethods CollectionsJoVE Encyclopedia of ExperimentsArchive
EDUCATION
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab ManualFaculty Resource CenterFaculty Site
Terms & Conditions of Use
Privacy Policy
Policies

Related Concept Videos

Mitochondrial Protein Sorting01:39

Mitochondrial Protein Sorting

4.2K
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...
4.2K
Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

3.0K
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,...
3.0K
Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

2.5K
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...
2.5K
Porin Insertion in the Outer Mitochondrial Membrane01:12

Porin Insertion in the Outer Mitochondrial Membrane

2.8K
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...
2.8K
Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

3.6K
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...
3.6K
Structure of Porins01:21

Structure of Porins

2.9K
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...
2.9K

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by
Same author

Decoding Outer Membrane β-Barrels: From Structural Curiosity to Engineered Nanotherapeutics.

Chemical reviews·2026
Same author

Linking multipoint folding and stability with functional regulation in the mitochondrial transmembrane β-barrel Sam50.

Nature communications·2026
Same author

Protein-lipid interplay governs ion channel gating and bioenergetics in human mitochondrial VDAC3.

Protein science : a publication of the Protein Society·2026
Same author

Synuclein and Mitochondrial Dysfunction: Regulating the Protein Import Complex toward PD Treatment?

ACS chemical neuroscience·2025
Same author

Lipid-regulated assembly mechanisms and functional energetics of the essential bacterial chaperone BamA.

Chemical science·2025
Same author

Conformational plasticity of mitochondrial VDAC2 controls the kinetics of its interaction with cytosolic proteins.

Science advances·2025
Same journal

Aromatic Cage-Directed Azide-Methyllysine Photochemistry for Profiling Nonhistone Interacting Partners of the MeCP2 Methyl-CpG-Binding Domain.

Biochemistry·2026
Same journal

Differential Hydroxypyruvate Processing by <i>E. coli</i> and <i>P. aeruginosa</i> DXP Synthases Reveals Preferential Xylulose 5-Phosphate Formation by the <i>P. aeruginosa</i> Enzyme.

Biochemistry·2026
Same journal

Structural and Functional Characterization of Heterologous Nitrogenase Complexes.

Biochemistry·2026
Same journal

Discovery of Bacterial Unspecific Peroxygenases.

Biochemistry·2026
Same journal

Lactate Biology: Subcellular Routing and Chemical Form Define Function.

Biochemistry·2026
Same journal

Nature's Anaerobic Toolkit: Glycyl Radical Enzymes and Their Expanding Functional and Mechanistic Diversity.

Biochemistry·2026
See all related articles

Related Experiment Video

Updated: Jun 4, 2025

Reconstitution of Msp1 Extraction Activity with Fully Purified Components
05:52

Reconstitution of Msp1 Extraction Activity with Fully Purified Components

Published on: August 10, 2021

2.4K

Mitochondrial Sorting and Assembly Machinery: Chaperoning a Moonlighting Role?

Roshika Ravi1, Deepsikha Routray1, Radhakrishnan Mahalakshmi1

  • 1Molecular Biophysics Laboratory, Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal 462066, India.

Biochemistry
|January 4, 2025
PubMed
Summary
This summary is machine-generated.

The Sorting and Assembly Machinery (SAM) protein, Sam50, is crucial for mitochondrial outer membrane protein assembly. Emerging evidence reveals Sam50 performs diverse primary roles beyond its known chaperone function.

Keywords:
MERCSSam50barrel biogenesislipid transportmembrane protein foldingmitochondrial chaperone

More Related Videos

Author Spotlight: Unveiling Mitochondrial Contact Sites and Architectural Insights
07:55

Author Spotlight: Unveiling Mitochondrial Contact Sites and Architectural Insights

Published on: June 16, 2023

1.3K
Rapid Isolation of the Mitoribosome from HEK Cells
09:33

Rapid Isolation of the Mitoribosome from HEK Cells

Published on: October 4, 2018

10.9K

Related Experiment Videos

Last Updated: Jun 4, 2025

Reconstitution of Msp1 Extraction Activity with Fully Purified Components
05:52

Reconstitution of Msp1 Extraction Activity with Fully Purified Components

Published on: August 10, 2021

2.4K
Author Spotlight: Unveiling Mitochondrial Contact Sites and Architectural Insights
07:55

Author Spotlight: Unveiling Mitochondrial Contact Sites and Architectural Insights

Published on: June 16, 2023

1.3K
Rapid Isolation of the Mitoribosome from HEK Cells
09:33

Rapid Isolation of the Mitoribosome from HEK Cells

Published on: October 4, 2018

10.9K

Area of Science:

  • Mitochondrial biology
  • Protein assembly
  • Cellular homeostasis

Background:

  • The mitochondrial outer membrane (OMM) houses beta-barrel proteins essential for cellular communication and homeostasis.
  • The Sorting and Assembly Machinery (SAM) complex, particularly its core component Sam50, facilitates the insertion and assembly of these proteins.
  • Sam50 has been traditionally viewed as a chaperone for OMM beta-barrel biogenesis.

Purpose of the Study:

  • To re-evaluate the primary functions of Sam50 beyond its established role in beta-barrel assembly.
  • To highlight the diverse and critical regulatory roles of SAM in maintaining mitochondrial and cellular health.

Main Methods:

  • Literature review and synthesis of recent research findings on Sam50.
  • Analysis of experimental data implicating Sam50 in various cellular processes.

Main Results:

  • Sam50 exhibits functions beyond beta-barrel assembly, including maintaining mitochondrial cristae morphology.
  • Sam50 is involved in lipid transport between the ER and mitochondria.
  • Sam50 plays roles in protein import, PINK1-Parkin pathway regulation, and programmed cell death.

Conclusions:

  • The SAM complex, particularly Sam50, has evolved multifaceted primary roles in eukaryotic cells.
  • Sam50's function extends far beyond a simple chaperone, acting as a key regulator of mitochondrial and cellular homeostasis.