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Related Concept Videos

Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

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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,...
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Structure of Porins01:21

Structure of Porins

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

Porin Insertion in the Outer Mitochondrial Membrane

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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...
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Mitochondrial Protein Sorting01:39

Mitochondrial Protein Sorting

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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...
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Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

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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...
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Mitochondrial Membranes01:45

Mitochondrial Membranes

16.4K
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,...
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Related Experiment Video

Updated: Dec 24, 2025

Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria
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Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria

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Systems Biochemistry Approaches to Defining Mitochondrial Protein Function.

Andrew Y Sung1, Brendan J Floyd2, David J Pagliarini3

  • 1Morgridge Institute for Research, Madison, WI, USA; Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA; School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA.

Cell Metabolism
|April 9, 2020
PubMed
Summary

Systems biochemistry combines large-scale and reductionist methods to define protein functions, particularly for mitochondria. This approach identifies new disease-related and essential mitochondrial proteins, advancing our understanding of mitochondrial biology and disease.

Keywords:
mitochondriamulti-omicsorphan proteinsrare diseasesystems biochemistry

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Author Spotlight: Unveiling Mitochondrial Contact Sites and Architectural Insights
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Analyzing Supercomplexes of the Mitochondrial Electron Transport Chain with Native Electrophoresis, In-gel Assays, and Electroelution
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Related Experiment Videos

Last Updated: Dec 24, 2025

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Author Spotlight: Unveiling Mitochondrial Contact Sites and Architectural Insights
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Analyzing Supercomplexes of the Mitochondrial Electron Transport Chain with Native Electrophoresis, In-gel Assays, and Electroelution
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Area of Science:

  • Biochemistry and Molecular Biology
  • Cellular Biology
  • Genomics and Proteomics

Background:

  • Defining the functions of all proteins is a major challenge in the post-genomic era, crucial for understanding biology and disease.
  • Traditional methods face barriers in characterizing poorly understood proteins.
  • Mitochondria present a well-defined proteome, ideal for comprehensive system analyses.

Purpose of the Study:

  • To leverage a combined approach, termed "systems biochemistry," to overcome limitations in protein function characterization.
  • To apply systems biochemistry to the mitochondrial system for a comprehensive understanding of its components and functions.
  • To accelerate the identification of disease-related and functionally important mitochondrial proteins.

Main Methods:

  • Integration of modern large-scale and classical reductionist experimental approaches.
  • Application of systems biochemistry to analyze the complete mitochondrial proteome.
  • Utilizing comprehensive analyses to position understudied proteins for mechanistic investigation.

Main Results:

  • Systems biochemistry has proven effective for characterizing mitochondrial proteins.
  • Accelerated identification of novel mitochondrial proteins linked to diseases.
  • Discovery of previously "missing" mitochondrial proteins with key functions.

Conclusions:

  • Systems biochemistry provides a powerful strategy to define protein functions, especially within complex cellular systems like mitochondria.
  • These advancements are crucial for a more complete understanding of mitochondrial activities.
  • The findings establish a molecular framework for investigating mitochondrial pathogenesis and related diseases.