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Related Concept Videos

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...
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...
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...
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...
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...
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...

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Related Experiment Video

Updated: May 23, 2026

From Constructs to Crystals &#8211; Towards Structure Determination of &#946;-barrel Outer Membrane Proteins
09:55

From Constructs to Crystals – Towards Structure Determination of β-barrel Outer Membrane Proteins

Published on: July 4, 2016

Predicting giant transmembrane β-barrel architecture.

Cyril F Reboul1, Khalid Mahmood, James C Whisstock

  • 1Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC 3800, Australia.

Bioinformatics (Oxford, England)
|April 3, 2012
PubMed
Summary
This summary is machine-generated.

Giant beta-barrel proteins, like cholesterol-dependent cytolysins (CDC), use a near-parallel strand arrangement (S=n/2). This differs from small beta-barrels (n≤24) where side-chain packing limits shear values.

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Last Updated: May 23, 2026

From Constructs to Crystals &#8211; Towards Structure Determination of &#946;-barrel Outer Membrane Proteins
09:55

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Published on: July 4, 2016

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Computational Prediction of Amino Acid Preferences of Potentially Multispecific Peptide-Binding Domains Involved in Protein-Protein Interactions
06:50

Computational Prediction of Amino Acid Preferences of Potentially Multispecific Peptide-Binding Domains Involved in Protein-Protein Interactions

Published on: January 26, 2024

Area of Science:

  • Structural biology
  • Biophysics
  • Protein folding

Background:

  • Beta-barrels are common protein structures involved in membrane pore formation.
  • Beta-barrel diameter is influenced by strand number (n) and shear (S).
  • Small beta-barrels (n≤24) have shear values typically between n and 2n.

Purpose of the Study:

  • To understand the structural basis of giant beta-barrel formation in cholesterol-dependent cytolysins (CDCs).
  • To investigate the proposed parallel strand arrangement (S=0) in giant beta-barrels.
  • To elucidate the architectural differences between small and giant beta-barrels.

Main Methods:

  • Comparison of molecular models with experimental data.
  • Analysis of side-chain packing within beta-barrel lumens.
  • Modeling of beta-barrel structures with varying strand numbers and shear degrees.

Main Results:

  • Giant CDC beta-barrels exhibit a 'near parallel' strand arrangement with S=n/2.
  • Side-chain packing limits shear values in small beta-barrels (n≤24).
  • Giant beta-barrels (n>24) lack these shear value limitations, enabling distinct architectures.

Conclusions:

  • Giant beta-barrels possess unique structural properties compared to smaller ones.
  • The 'near parallel' arrangement in giant beta-barrels facilitates membrane spanning.
  • Understanding these structural differences is key to comprehending CDC function.