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Related Concept Videos

Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

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Nuclear encoded mitochondrial precursors are imported to the inner membrane in a multistep process involving two separate translocons, TIM22 and TIM23. TIM23 is a cation-selective pore that remains closed by the N terminal segment of the protein. Negative charges on the TIM23 act as a receptor for the incoming precursor, pulling the positively charged matrix-targeting sequence for peptide insertion and translocation.
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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.
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 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.
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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

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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.
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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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Updated: Mar 12, 2026

Assessment of Submitochondrial Protein Localization in Budding Yeast Saccharomyces cerevisiae
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A mitochondrial insertion directs substrate selection and engagement by ClpX.

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    Summary
    This summary is machine-generated.

    The mitochondrial insertion (MI) in ClpX protein unfoldases is crucial for recruiting and activating substrates like ALAS. This domain aids in substrate processing by the AAA+ motor, impacting protein degradation pathways.

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    Area of Science:

    • Biochemistry
    • Molecular Biology
    • Cell Biology

    Background:

    • Protein unfoldases, like ClpX, utilize AAA+ ATPase domains for function.
    • Accessory domains modulate substrate specificity and interactions.
    • Mitochondrial ClpX homologs possess a unique insertion (MI) absent in bacterial counterparts.

    Purpose of the Study:

    • To investigate the role of the mitochondrial insertion (MI) in the function of mitochondrial ClpX.
    • To determine if the MI directs interactions with mitochondrial substrates, specifically ALAS.
    • To elucidate the MI's contribution to substrate recruitment, activation, and processing.

    Main Methods:

    • Site-directed mutagenesis to assess the impact of MI truncation and specific mutations.
    • Enzyme activity assays to measure ATPase activity and substrate activation.
    • In vitro degradation assays using model substrates like casein and ALAS.

    Main Results:

    • The MI is essential for the recruitment and activation of ALAS by yeast ClpX.
    • The MI's role in ALAS degradation by human CLPXP is context-dependent (adaptor-mediated vs. independent).
    • MI truncation moderately affects ATPase activity but can be uncoupled from substrate activation efficiency.

    Conclusions:

    • The MI is a key functional domain in mitochondrial ClpX, facilitating substrate recruitment and accelerating AAA+ motor processing.
    • The MI plays a critical role in the efficient degradation of specific mitochondrial substrates like ALAS.
    • Understanding the MI's function provides insights into mitochondrial protein quality control and homeostasis.