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Related Concept Videos

The ADP/ATP Carrier Protein01:42

The ADP/ATP Carrier Protein

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ADP/ATP carrier or AAC protein is the most abundant carrier protein in the inner mitochondrial membrane. It transports large quantities of ADP and ATP, equivalent to the average human body weight, every day. Among other transporters, ACC protein is one of the best-studied members of the mitochondrial carrier protein family. The ADP/ATP carrier protein comprises two transmembrane helices connected to a loop and a single alpha-helix on the matrix side. It switches between two conformational...
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Mitochondrial Protein Sorting01:39

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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.
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Protein Transport into the Inner Mitochondrial Membrane01:34

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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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Cholesterol: Significance and Regulation01:29

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Although not a source of energy, cholesterol plays a significant role as a foundational structure for bile salts, steroid hormones, and vitamin D, as well as being a crucial component of plasma membranes. Approximately 15% of blood cholesterol is derived from our diet, with the remainder synthesized from acetyl CoA by the liver and intestines. Cholesterol is eliminated from the body through its conversion into bile salts, which are eventually discarded in the feces.
Considering cholesterol and...
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Regulation of Nuclear Protein Sorting01:45

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Nuclear protein sorting regulates nucleus composition and gene expression, crucial for determining the fate of a eukaryotic cell. Hence, the entry and exit of molecules across the nuclear envelope is a tightly controlled process. Nuclear protein sorting can be inhibited by one of the following ways: 1) masking cargo signal sequences, 2) modifying the nuclear receptor's affinity for cargo, 3) controlling the nuclear pore size, 4) retaining the cargo during its transit to the cytosol or the...
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Related Experiment Video

Updated: Dec 13, 2025

Author Spotlight: An Optimized Automated Method for Investigating Retinoic Acid Receptors in Neuronal Mitochondria
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Aster-B coordinates with Arf1 to regulate mitochondrial cholesterol transport.

John-Paul Andersen1, Jun Zhang1, Haoran Sun2

  • 1Sam and Ann Barshop Institute for Longevity and Aging Studies, Department of Pharmacology, University of Texas Health Science Center at San Antonio, Texas Research Park Campus - MC 7755, 15355 Lambda Drive, San Antonio, TX, 78245, USA.

Molecular Metabolism
|August 2, 2020
PubMed
Summary

Aster-B protein is crucial for transporting cholesterol to mitochondria, impacting steroidogenesis and cellular respiration. Its deficiency disrupts mitochondrial function by impairing cholesterol and fatty acid uptake.

Keywords:
Arf1Cholesterol transportFatty acidsGRAMD1bMitochondria

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Area of Science:

  • Cell Biology
  • Biochemistry
  • Molecular Biology

Background:

  • Cholesterol is vital for mitochondrial functions including steroidogenesis, membrane integrity, and respiration.
  • Mitochondria require cholesterol replenishment from other cellular membranes due to their naturally low cholesterol content.
  • The precise molecular mechanisms of mitochondrial cholesterol transport are not fully understood.

Purpose of the Study:

  • To investigate the function of the Aster-B gene in mediating cholesterol transport to mitochondria.
  • To elucidate the underlying molecular mechanisms of Aster-B in mitochondrial cholesterol trafficking.

Main Methods:

  • CRISPR/Cas9 gene editing to create Aster-B deficient cell lines.
  • Confocal imaging and biochemical assays to assess mitochondrial cholesterol transport.
  • Deletion mutational analysis of the Aster-B N-terminal mitochondrial targeting sequence (MTS).

Main Results:

  • Aster-B deficiency significantly reduced mitochondrial cholesterol content by impairing ER-to-mitochondria transport.
  • Aster-B is essential for transporting fatty acids derived from cholesterol ester hydrolysis to mitochondria.
  • The N-terminal MTS of Aster-B is critical for mitochondrial targeting and cholesterol uptake; its deletion or Arf1 GTPase ablation blocked transport and caused mitochondrial dysfunction.

Conclusions:

  • Aster-B is identified as a key regulator of cholesterol transport from the ER to mitochondria.
  • Aster-B coordinates mitochondrial cholesterol and fatty acid uptake, positioning it as a novel regulator of steroidogenesis.