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Related Concept Videos

Pinocytosis00:43

Pinocytosis

62.7K
Cells use energy-requiring bulk transport mechanisms to transfer large particles, or large amounts of small particles, into or out of the cell. The cells envelop the particles in spherical membranes called vesicles or vacuoles. Vesicles that transport material into the cell are built from the cell membrane. These vesicles encapsulate external molecules and transport them into the cell in a process called endocytosis.
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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.
Transport of mitochondrial precursors across the TIM23 channel is driven by...
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Protein Transport to the Stroma01:24

Protein Transport to the Stroma

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Chloroplasts are triple membrane structures with an outer membrane, an inner membrane, and a thylakoid membrane, each containing distinct metabolite transporters, membrane translocons, and enzymes. Appropriate sorting and translocating these proteins to their correct membrane systems is essential for chloroplast function.
Protein complexes called the translocon of the outer chloroplast membrane or TOC complex, and the translocon of the inner chloroplast membrane or TIC complex mediate the...
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Protein Transport to the Outer Chloroplast Membrane01:11

Protein Transport to the Outer Chloroplast Membrane

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Chloroplast outer membrane proteins encoded by the nucleus are synthesized in the cytosol. Soon after synthesis, they bind cytosolic factors such as 14-3-3 protein and the Hsp70 chaperones that keep these precursors in an unfolded state until their translocation.
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.
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Protein Import into the Peroxisomes01:27

Protein Import into the Peroxisomes

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Cells contain membrane-bound organelles called peroxisomes that oxidize organic molecules by transferring hydrogen atoms to oxygen, producing hydrogen peroxide. Peroxisomes enzymatically convert the released hydrogen peroxide into water and oxygen.
Peroxisomal Protein Import:
Peroxisomes lack the genetic machinery required to code for their own proteins. Hence, most peroxisomal membrane, lumenal and transmembrane proteins are synthesized in the cytoplasm or ER and transported to the peroxisome...
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Protein Transport to the Inner Chloroplast Membrane01:18

Protein Transport to the Inner Chloroplast Membrane

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Proteins targeted to the inner chloroplast membrane, or plastid proteins, are transported by two general pathways: the stop-transfer and the re-insertion or post-import pathways. Most plastid proteins carry N-terminal transit sequences and internal import sequences targeting it to the specific chloroplast subcompartment. Proteins targeted by the stop-transfer pathway have internal hydrophobic sequences that inhibit their translocation into the stroma. As a result, these precursors are arrested...
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Related Experiment Video

Updated: May 5, 2026

Using Caco-2 Cells to Study Lipid Transport by the Intestine
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Using Caco-2 Cells to Study Lipid Transport by the Intestine

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Molecular chaperones in cellular protein folding

F U Hartl1

  • 1Howard Hughes Medical Institute, Memorial Sloan-Kettering Cancer Center, New York 10021, USA.

Nature
|June 13, 1996
PubMed
Summary

Molecular chaperones are essential proteins that prevent misfolded protein structures in cells. The Hsp70 and chaperonin families use ATP-dependent mechanisms to assist in protein folding, especially under stress.

Area of Science:

  • Cellular biology
  • Biochemistry
  • Protein folding

Background:

  • Newly synthesized proteins require assistance for proper folding within the cell.
  • Molecular chaperones are conserved proteins crucial for preventing protein misfolding.
  • Cellular stress, such as heat shock, increases the risk of protein misfolding.

Purpose of the Study:

  • To summarize the understanding of molecular chaperone mechanisms in protein folding.
  • To highlight the roles of Hsp70 and chaperonin families.
  • To describe the cooperative function of chaperones in assisting new polypeptide chains.

Main Methods:

  • Review of existing literature on molecular chaperones.
  • Analysis of ATP-dependent mechanisms.
  • Examination of chaperone cooperation in protein folding.

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Membrane Transport Processes Analyzed by a Highly Parallel Nanopore Chip System at Single Protein Resolution

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Biotinylated Cell-penetrating Peptides to Study Intracellular Protein-protein Interactions
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Biotinylated Cell-penetrating Peptides to Study Intracellular Protein-protein Interactions

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Related Experiment Videos

Last Updated: May 5, 2026

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Membrane Transport Processes Analyzed by a Highly Parallel Nanopore Chip System at Single Protein Resolution
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Main Results:

  • Molecular chaperones prevent misfolded protein structures under normal and stress conditions.
  • Hsp70 and chaperonin families utilize ATP-dependent mechanisms for protein folding.
  • These chaperone families can cooperate to facilitate the folding of new polypeptide chains.

Conclusions:

  • Molecular chaperones are vital for maintaining proteostasis.
  • ATP-dependent mechanisms are central to chaperone function.
  • Cooperative action of chaperones enhances their efficiency in protein folding.