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Related Concept Videos

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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Mitochondrial Precursor Proteins01:39

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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.
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Translocation of Proteins into the Mitochondria01:19

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Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
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Among all the organelles in an animal cell, only mitochondria have their own independent genomes. Animal mitochondrial DNA is a double-stranded, closed-circular molecule with around 20,000 base pairs. Mitochondrial DNA is unique in that one of its two strands, the heavy, or H, -strand is guanine rich, whereas the complementary strand is cytosine rich and called the light, or L, -strand. Compared to nuclear DNA, mitochondrial DNA has a very low percentage of non-coding regions and is marked by...
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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.
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Molecular Chaperones and Protein Folding03:00

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The native conformation of a protein is formed by interactions between the side chains of its constituent amino acids. When the amino acids cannot form these interactions, the protein cannot fold by itself and needs chaperones. Notably, chaperones do not relay any additional information required for the folding of polypeptides; the native conformation of a protein is determined solely by its amino acid sequence. Chaperones catalyze protein folding without being a part of the folded protein.
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[Mitochondrial Hsp70 - function and evolution].

Jaroslaw Marszalek1

  • 1Laboratory of Evolutionary Biochemistry, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, 8 Antoniego Abrahama St., 80-307 Gdansk, Poland.

Postepy Biochemii
|January 30, 2017
PubMed
Summary

Heat shock protein 70 (Hsp70) molecular chaperones and their co-chaperones (J-proteins and nucleotide release factors) manage protein functions. Yeast mitochondria reveal how Hsp70 systems evolve specialized roles for diverse cellular tasks.

Keywords:
J-protein co-chaperonesiron-sulfur clustersmitochondrial DNAmitochondrial protein importprotein evolution

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Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Biochemistry

Background:

  • Hsp70 molecular chaperones are essential for critical cellular processes like protein folding and translocation.
  • Hsp70 systems comprise a core Hsp70 protein, J-proteins, and nucleotide release factors (NRFs) that regulate substrate interaction cycles.
  • Eukaryotic cells utilize multiple Hsp70s, J-proteins, and NRFs, enabling diverse cellular functions through specialization or multifunctional interactions.

Purpose of the Study:

  • To explore the functional divergence and evolution of Hsp70 machineries within cellular compartments.
  • To highlight the role of co-chaperones in regulating Hsp70 ATPase activity and substrate interactions.
  • To use yeast mitochondrial Hsp70 systems as a model for understanding Hsp70 system complexity.

Main Methods:

  • Analysis of Hsp70 system components and their interactions.
  • Investigating the regulatory roles of J-proteins and NRFs in the Hsp70 chaperone cycle.
  • Comparative study of Hsp70 systems in yeast mitochondria.

Main Results:

  • Hsp70 systems achieve functional diversity through specialized Hsp70 proteins or the interaction of multifunctional Hsp70s with various J-proteins.
  • J-proteins stimulate Hsp70 ATPase activity, while NRFs promote nucleotide exchange, controlling substrate binding and release.
  • Yeast mitochondrial Hsp70 systems exemplify functional divergence and the evolutionary adaptation of chaperone machineries.

Conclusions:

  • The interplay between Hsp70s and their specialized co-chaperones is crucial for cellular protein homeostasis.
  • Functional specialization within Hsp70 systems allows for adaptation to diverse cellular environments and tasks.
  • The study of yeast mitochondria provides valuable insights into the evolution and functional diversification of molecular chaperone systems.