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Related Concept Videos

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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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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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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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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Protein Folding Quality Check in the RER01:29

Protein Folding Quality Check in the RER

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ER is the primary site for the maturation and folding of soluble and transmembrane secretory proteins. The calnexin cycle is a specific chaperone system that folds and assesses the confirmation of N-glycosylated proteins before they can exit the ER lumen. The primary players of this quality check pipeline are the lectins, ER-resident chaperones, and a glucosyl transferase enzyme. In case the calnexin system in the lumen fails to salvage a misfolded protein, it is transported to the cytoplasm...
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Improving Translational Accuracy02:07

Improving Translational Accuracy

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Base complementarity between the three base pairs of mRNA codon and the tRNA anticodon is not a failsafe mechanism. Inaccuracies can range from a single mismatch to no correct base pairing at all. The free energy difference between the correct and nearly correct base pairs can be as small as 3 kcal/ mol. With complementarity being the only proofreading step, the estimated error frequency would be one wrong amino acid in every 100 amino acids incorporated. However, error frequencies observed in...
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Related Experiment Video

Updated: Jul 4, 2025

Isolation of mRNAs Associated with Yeast Mitochondria to Study Mechanisms of Localized Translation
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Isolation of mRNAs Associated with Yeast Mitochondria to Study Mechanisms of Localized Translation

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Mitochondrial protein synthesis quality control.

Lidiia Koludarova1, Brendan J Battersby1

  • 1Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki 00014, Finland.

Human Molecular Genetics
|January 27, 2024
PubMed
Summary
This summary is machine-generated.

Mitochondrial protein synthesis quality control ensures organelle homeostasis by eliminating errors in gene expression. This review explores defects and the surveillance pathways that maintain mitochondrial integrity.

Keywords:
AFG3L2MTRFROMA1OPA1OXA1LRNA processingcell stressco-translational quality controlfusion open reading framesmembrane morphologymitochondrianon-stop mRNApost-transcriptionalprotein synthesisproteostasisribosome quality controlribosomes

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Area of Science:

  • Cellular Biology
  • Molecular Biology
  • Genetics

Background:

  • Human mitochondrial DNA (mtDNA) is a simplified genome enabling compartmentalized gene expression.
  • Transcription and translation occur without physical separation in mitochondria, lacking apparent quality control for faulty mRNA.
  • Mitochondrial ribosomes synthesize 13 essential hydrophobic proteins requiring co-translational insertion into the inner membrane.

Purpose of the Study:

  • To explore defects in mitochondrial protein synthesis arising from gene expression errors.
  • To examine the quality control processes that eliminate mistakes and maintain organelle homeostasis.
  • To provide an integrated view of mitochondrial protein synthesis quality control and suggest future research directions.

Main Methods:

  • Review of existing literature on mitochondrial gene expression and protein synthesis.
  • Analysis of known quality control mechanisms within the mitochondrial environment.
  • Integration of data to understand the stepwise elimination of protein synthesis errors.

Main Results:

  • Defects in mitochondrial protein synthesis can originate from various gene expression errors.
  • Stepwise quality control mechanisms are essential for preventing perturbations in organelle homeostasis.
  • Responsive quality control is critical for maintaining the integrity of the inner mitochondrial membrane.

Conclusions:

  • Mitochondrial protein synthesis is susceptible to errors, necessitating robust quality control.
  • Existing quality control pathways are crucial for maintaining mitochondrial function and integrity.
  • Further research is needed to fully elucidate and potentially enhance these quality control mechanisms.