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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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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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Energy to Drive Translocation01:37

Energy to Drive Translocation

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Mitochondrial protein import is powered by two distinct energy sources: ATP hydrolysis and electrochemical potential across the inner membrane. Newly synthesized precursors are bound by cytosolic chaperones of the Hsp70 family, which guide them to the import receptors on the mitochondrial surface. Utilizing the energy of ATP hydrolysis, Hsp70 chaperones transfer these precursors to the TOM receptors on the mitochondrial outer membrane.
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Assessment of Submitochondrial Protein Localization in Budding Yeast Saccharomyces cerevisiae
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The extensive and functionally uncharacterized mitochondrial phosphoproteome.

Natalie M Niemi1, David J Pagliarini2

  • 1Department of Biochemistry & Molecular Biophysics, Washington University in St Louis, St Louis, Missouri, USA.

The Journal of Biological Chemistry
|June 18, 2021
PubMed
Summary
This summary is machine-generated.

Mitochondrial protein phosphorylation is crucial for metabolism, but many sites are uncharacterized. This study maps phosphorylation and proposes how it impacts mitochondrial function and homeostasis.

Keywords:
mitochondriaphosphoproteomicsprotein kinaseprotein phosphataseprotein phosphorylation

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Area of Science:

  • Biochemistry
  • Cell Biology
  • Metabolomics

Background:

  • Reversible protein phosphorylation was historically linked to mitochondrial metabolism.
  • Advances in mass spectrometry have identified numerous mitochondrial phosphorylation sites, yet most remain functionally uncharacterized.
  • Mitochondrial protein phosphatases are essential for metabolic homeostasis, underscoring the importance of phosphorylation regulation.

Purpose of the Study:

  • To map the landscape of protein phosphorylation in mammalian mitochondria.
  • To identify the known functions of mitochondrial-resident phosphatases.
  • To propose mechanisms by which mitochondrial phosphorylation influences organellar function.

Main Methods:

  • Curation of publicly available phosphoproteomics datasets.
  • Bioinformatic analysis of identified phosphorylation sites.
  • Literature review of mitochondrial phosphatase functions.

Main Results:

  • A comprehensive map of mitochondrial protein phosphorylation sites was generated.
  • Key mitochondrial phosphatases and their roles in metabolic regulation were highlighted.
  • Potential functional impacts of phosphorylation on enzyme activity, protein import, and homeostasis were proposed.

Conclusions:

  • Mitochondrial protein phosphorylation is extensive and critical for cellular function.
  • Understanding these modifications is vital for comprehending mitochondrial and organismal homeostasis.
  • Further research into the functional roles of mitochondrial phosphorylation is warranted.