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Related Concept Videos

Mechanisms of Membrane Domain Formation00:59

Mechanisms of Membrane Domain Formation

Different physical properties of lipids and proteins allow them to localize and form distinct islands or domains in the membrane. Some membrane domains are formed due to protein-protein interactions, whereas others are formed due to the presence of specific lipids such as sphingolipids and sterols—for example, large proteins, such as bacteriorhodopsin, aggregate and create distinct domains.
Another mechanism for membrane domain formation involves membrane proteins interacting with cytoskeletal...
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...
Cotranslational Protein Translocation01:20

Cotranslational Protein Translocation

Translocation of proteins across membranes is an ancient process that occurs even in bacteria and archaebacteria. In fact, the components of the translocation machinery are still conserved between prokaryotes and eukaryotes.
Sec61 channel partners for cotranslational translocation
During cotranslational translocation, the Sec61 channel partners with the signal recognition particle (SRP), the signal recognition particle receptor (SR), and the ribosomes to transport the nascent polypeptide chain...
Structure of Porins01:21

Structure of Porins

Mitochondria, chloroplasts, and gram-negative bacteria have transmembrane, beta-barrel proteins called porins to mediate the free diffusion of ions and metabolites across the membrane. Mitochondrial porin precursors contain conserved amino acid sequences called beta signals at their C-terminal. Beta signals have a  motif of PoXGXXHyXHy (Po-Polar, X-Any amino acid, G-Glycine, Hy-LargeHydrophobic), which are crucial for precursor recognition to initiate precursor assembly. Beta-barrel precursors...
Porin Insertion in the Outer Mitochondrial Membrane01:12

Porin Insertion in the Outer Mitochondrial Membrane

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.
Three models describe the assembly of porins by the SAM complex and their insertion into the outer membrane. Model 1 suggests that porins are assembled outside the SAM channel as the...

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Related Experiment Video

Updated: Jun 6, 2026

Single-Molecule Imaging of Lateral Mobility and Ion Channel Activity in Lipid Bilayers using Total Internal Reflection Fluorescence (TIRF) Microscopy
08:55

Single-Molecule Imaging of Lateral Mobility and Ion Channel Activity in Lipid Bilayers using Total Internal Reflection Fluorescence (TIRF) Microscopy

Published on: February 17, 2023

Outer membrane translocons: structural insights into channel formation.

Vijaykumar Karuppiah1, Jamie-Lee Berry, Jeremy P Derrick

  • 1Faculty of Life Sciences, The University of Manchester, Oxford Road, Manchester, UK.

Trends in Microbiology
|December 7, 2010
PubMed
Summary
This summary is machine-generated.

Gram-negative bacteria use outer membrane proteins (OMPs) to maintain cell integrity and secrete molecules. Recent studies reveal diverse OMP structures, including beta-barrels and alpha-helices, impacting macromolecule transport.

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Transmembrane Domain Oligomerization Propensity determined by ToxR Assay
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Transmembrane Domain Oligomerization Propensity determined by ToxR Assay

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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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Related Experiment Videos

Last Updated: Jun 6, 2026

Single-Molecule Imaging of Lateral Mobility and Ion Channel Activity in Lipid Bilayers using Total Internal Reflection Fluorescence (TIRF) Microscopy
08:55

Single-Molecule Imaging of Lateral Mobility and Ion Channel Activity in Lipid Bilayers using Total Internal Reflection Fluorescence (TIRF) Microscopy

Published on: February 17, 2023

Transmembrane Domain Oligomerization Propensity determined by ToxR Assay
06:45

Transmembrane Domain Oligomerization Propensity determined by ToxR Assay

Published on: May 26, 2011

Production of Disulfide-stabilized Transmembrane Peptide Complexes for Structural Studies
12:05

Production of Disulfide-stabilized Transmembrane Peptide Complexes for Structural Studies

Published on: March 6, 2013

Area of Science:

  • Microbiology
  • Structural Biology
  • Biochemistry

Background:

  • Gram-negative bacteria possess a complex outer membrane essential for cellular integrity and regulating the transport of molecules.
  • Outer membrane proteins (OMPs) play a critical role in maintaining this barrier and facilitating the secretion of various substances, including toxins.

Purpose of the Study:

  • To review recent structural studies on outer membrane proteins involved in macromolecule transport across the Gram-negative bacterial outer membrane.
  • To elucidate the structural mechanisms underlying the passage of proteins and other macromolecules through these outer membrane components.

Main Methods:

  • Analysis of recent high-resolution structural data (e.g., X-ray crystallography, cryo-electron microscopy) of outer membrane proteins.
  • Comparative structural analysis of different classes of outer membrane protein secretion systems.

Main Results:

  • Identified two major structural classes of outer membrane proteins involved in transport: classical beta-barrel structures and those utilizing transmembrane alpha-helices.
  • Demonstrated that beta-barrel OMPs facilitate substrate passage through conformational changes within the barrel lumen.
  • Highlighted distinct mechanisms for secretion systems employing alpha-helical OMP components.

Conclusions:

  • Recent structural insights reveal diverse mechanisms for macromolecule transport across the Gram-negative outer membrane.
  • The structural diversity of OMPs, including beta-barrels and alpha-helices, reflects distinct functional adaptations for secretion.
  • Further structural studies are crucial for a comprehensive understanding of bacterial outer membrane transport systems.