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Related Concept Videos

Mitochondrial Protein Sorting01:39

Mitochondrial Protein Sorting

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...
Molecular Chaperones and Protein Folding03:00

Molecular Chaperones and Protein Folding

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.
The...
Molecular Chaperones and Protein Folding03:00

Molecular Chaperones and Protein Folding

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.
The...
Energy to Drive Translocation01:37

Energy to Drive Translocation

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.
Generally, polypeptides are unfolded by two distinct...
Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

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 precursors...
Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

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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Defining Hsp33's Redox-regulated Chaperone Activity and Mapping Conformational Changes on Hsp33 Using Hydrogen-deuterium Exchange Mass Spectrometry
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Mitochondrial ATP-independent chaperones.

Nikos Petrakis1, Felicity Alcock, Kostas Tokatlidis

  • 1Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas (IMBB-FORTH), Heraklion, Crete, Greece.

IUBMB Life
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PubMed
Summary

Small Tims, mitochondrial chaperones, escort proteins to membranes without energy. Their structure enables this vital function in all eukaryotes, crucial for mitochondrial protein insertion.

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Area of Science:

  • Mitochondrial biology
  • Protein transport
  • Cellular biochemistry

Background:

  • Mitochondria have a specialized chaperone system in the intermembrane space.
  • Small Tims are found in all eukaryotes, from yeast to humans.
  • These chaperones are essential for inserting proteins into mitochondrial membranes.

Purpose of the Study:

  • To discuss the structural properties of small Tims.
  • To elucidate the relationship between small Tim structure and their chaperoning function.
  • To highlight their ATP-independent mechanism.

Main Methods:

  • Structural analysis of small Tims.
  • Functional studies of protein escorting.
  • Comparative analysis with other ATP-independent chaperones.

Main Results:

  • Small Tims possess unique structural features.
  • These structures facilitate the energy-independent escort of proteins.
  • Structural similarities exist with other ATP-independent chaperones.

Conclusions:

  • The structure of small Tims is intrinsically linked to their chaperoning role.
  • They represent an efficient, ATP-independent mechanism for mitochondrial protein targeting.
  • Understanding small Tim structure provides insights into mitochondrial protein homeostasis.