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Related Concept Videos

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...
Single-pass Transmembrane Proteins01:25

Single-pass Transmembrane Proteins

Integral membrane proteins are tightly associated with the cell membrane and play a crucial role in cell communication, signaling, adhesion, and transport of the molecules. Some integral membrane proteins are present only in the membrane monolayer. For example, the enzyme fatty acid amide hydrolase is present in the cytoplasmic side of the membrane monolayer. In contrast, another type of integral membrane protein, also known as a transmembrane protein, spans across the membrane. Transmembrane...
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.
Insertion of Single-pass Transmembrane Proteins in the RER01:26

Insertion of Single-pass Transmembrane Proteins in the RER

Integral membrane proteins are proteins adhered to the lipid bilayer of a cell organelle or membrane. They can be of two types: transmembrane integral proteins that span the lipid bilayer and monotopic proteins that are attached to either side of the membrane but do not pass through it.
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
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...
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...

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Related Experiment Video

Updated: Jul 4, 2026

Transmembrane Domain Oligomerization Propensity determined by ToxR Assay
06:45

Transmembrane Domain Oligomerization Propensity determined by ToxR Assay

Published on: May 26, 2011

How translocons select transmembrane helices.

Stephen H White1, Gunnar von Heijne

  • 1Department of Physiology and Biophysics, University of California, Irvine, California 92697-4560, USA. stephen.white@uci.edu

Annual Review of Biophysics
|June 25, 2008
PubMed
Summary
This summary is machine-generated.

Hydrophobic membrane proteins require the translocon machine for insertion into cellular membranes. Recent advances clarify translocon mechanisms and the physical chemistry governing membrane protein stability and insertion.

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Last Updated: Jul 4, 2026

Transmembrane Domain Oligomerization Propensity determined by ToxR Assay
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Method to Visualize and Analyze Membrane Interacting Proteins by Transmission Electron Microscopy
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Production of Disulfide-stabilized Transmembrane Peptide Complexes for Structural Studies
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Production of Disulfide-stabilized Transmembrane Peptide Complexes for Structural Studies

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Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • Membrane proteins, essential for cellular functions, face aggregation challenges due to hydrophobicity.
  • Ribosomes synthesize membrane proteins, but auxiliary machinery is needed for proper insertion.

Purpose of the Study:

  • To review recent progress in understanding membrane protein insertion.
  • To connect physical principles of membrane protein stability with translocon function.
  • To elucidate the mechanisms of translocon-mediated transmembrane helix insertion.

Main Methods:

  • Review of recent scientific literature.
  • Analysis of physical chemistry principles governing protein-lipid interactions.
  • Examination of translocon structure and function.

Main Results:

  • Significant progress in understanding membrane protein stability and translocon mechanisms.
  • Insights into how the translocon selects and inserts transmembrane helices.
  • Established connection between thermodynamic equilibrium and protein structure.

Conclusions:

  • The translocon is crucial for orderly membrane protein insertion.
  • Physicochemical interactions dictate membrane protein structure and stability.
  • Understanding these principles advances knowledge of membrane protein biogenesis.