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Related Concept Videos

Protein Translocation Machinery on the ER Membrane01:28

Protein Translocation Machinery on the ER Membrane

The translocon complex situated on the ER membrane is the main gateway for the protein secretory pathway. It facilitates the transport of nascent peptides into the ER lumen and their insertion into the ER membrane.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the translocon complex.
Multi-pass Transmembrane Proteins and β-barrels01:09

Multi-pass Transmembrane Proteins and β-barrels

In multi-pass transmembrane proteins, the polypeptide chain crosses the membrane more than once. The transmembrane polypeptide chain either forms an α-helix or β-strand structure. α-Helix containing multi-pass transmembrane proteins are ubiquitous, whereas β-strand containing ones are mainly found in gram-negative bacteria, mitochondria, and chloroplasts.
α-Helix containing multi-pass transmembrane proteins
Multi-pass transmembrane proteins such as G-protein-linked receptors (GPCRs) and...
Insertion of Multi-pass Transmembrane Proteins in the RER01:29

Insertion of Multi-pass Transmembrane Proteins in the RER

The rough ER membrane synthesizes, assembles, and embeds transmembrane proteins in diverse topologies. These proteins function as transporters or channels and can remain in the ER membrane or are sent to the Golgi complex, lysosome, and cell membrane.
The multipass transmembrane proteins are the type IV integral membrane proteins with multiple topogenic sequences determining their spatial arrangement in the ER membrane. Nearly all multipass proteins lack a cleavable signal sequence and use...
Overview of Protein Sorting and Transport01:45

Overview of Protein Sorting and Transport

Eukaryotic cells have different membrane-bound organelles with distinct protein requirements. The process by which proteins are targeted to a specific organelle is called protein sorting.
Protein sorting can be of two types: signal-based sorting and vesicle-based trafficking. In signal-based sorting, specific amino acid sequences called sorting signals target proteins to the proper location inside the cell either via gated transport or by protein translocation.  In gated transport, folded...
Post-translational Translocation of Proteins to the RER01:27

Post-translational Translocation of Proteins to the RER

A sizable fraction of proteins destined for ER are first synthesized in the cell cytosol and then transported across the ER membrane–a process called post-translational translocation. Similar to cotranslationally translocated proteins, these proteins also use the Sec translocon complex to enter the ER lumen.
Targeting proteins to the ER
Hsp40 and Hsp70 chaperone molecules bind the translated proteins in the cytosol to prevent their folding. The chaperone binding helps to keep the signal...
Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

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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Related Experiment Video

Updated: Jun 10, 2026

Membrane Transport Processes Analyzed by a Highly Parallel Nanopore Chip System at Single Protein Resolution
11:55

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

Published on: August 16, 2016

Polymer translocation through pores with complex geometries.

Aruna Mohan1, Anatoly B Kolomeisky, Matteo Pasquali

  • 1Department of Chemistry, Rice University, Houston, Texas 77005, USA.

The Journal of Chemical Physics
|July 17, 2010
PubMed
Summary
This summary is machine-generated.

We developed a new theoretical method to study polymer translocation through complex composite pores. Reverse chain motions significantly impact translocation time, and introducing polymers on the wider side speeds up the process.

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Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

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Last Updated: Jun 10, 2026

Membrane Transport Processes Analyzed by a Highly Parallel Nanopore Chip System at Single Protein Resolution
11:55

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

Published on: August 16, 2016

Single-Molecule Diffusion and Assembly on Polymer-Crowded Lipid Membranes
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Single-Molecule Diffusion and Assembly on Polymer-Crowded Lipid Membranes

Published on: July 19, 2022

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
06:55

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

Published on: September 26, 2016

Area of Science:

  • Polymer physics
  • Theoretical chemistry
  • Nanopore science

Background:

  • Polymer translocation through nanopores is crucial for biological processes and nanotechnology.
  • Understanding translocation dynamics in complex pore geometries remains a challenge.
  • Existing models often simplify pore structures, neglecting intricate details.

Purpose of the Study:

  • To develop a versatile theoretical framework for investigating polymer translocation through composite pores of arbitrary geometries.
  • To analyze the impact of reverse chain motions at pore interfaces on translocation dynamics.
  • To provide insights into optimizing translocation efficiency in engineered nanopore systems.

Main Methods:

  • A novel theoretical method was developed to model polymer translocation.
  • The method explicitly accounts for reverse chain motions at the junctions of composite pores.
  • Simulations were performed for polymer translocation between spherical compartments connected by cylindrical and composite (two-cylinder) pores.

Main Results:

  • Reverse chain motions at pore interfaces can significantly influence the total translocation time.
  • Translocation through a two-cylinder composite pore is faster when initiated from the wider (cis) side compared to the narrower (trans) side.
  • The proposed method successfully models translocation in complex geometries, including structures resembling the alpha-hemolysin channel.

Conclusions:

  • The developed theoretical method offers a powerful tool for studying polymer translocation in complex systems.
  • Understanding and controlling reverse chain motions are critical for manipulating translocation dynamics.
  • Pore geometry and entry-side selection are key factors in optimizing polymer translocation efficiency.