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Related Concept Videos

Integrins01:10

Integrins

Animal and protozoan cells do not have cell walls to help maintain shape and provide structural stability. Instead, these eukaryotic cells secrete a sticky mass of carbohydrates and proteins into the spaces between adjacent cells. This network of proteins and molecules is called an extracellular matrix or ECM.
Some ECM proteins assemble into a basement membrane to which the remaining components adhere. Proteoglycans typically form the bulk of the ECM while fibrous proteins, like collagen,...
Activation of Integrins01:15

Activation of Integrins

Integrins bind ligands and transmit information from outside the cell to inside or vice-versa through an "outside-in signaling" or "inside-out signaling."
In "outside-in signaling," external factors in the extracellular space bind to exposed ligand binding sites on integrins. This causes the inactive protein to undergo a conformational change to become active. Integrins are often clustered on the cell membrane. Repetitive and regularly spaced ligand binding events provide an effective stimulus.
Intracellular Signaling Affects Focal Adhesions01:17

Intracellular Signaling Affects Focal Adhesions

Integrins act both as extracellular input receivers and as intracellular processing activators. As their name suggests, integrins are entirely integrated into the membrane structure. Their hydrophobic membrane-spanning regions interact with the phospholipid bilayer's hydrophobic region. These membrane receptors provide extracellular attachment sites for effectors like hormones and growth factors. They activate intracellular response cascades when their effectors are bound and active.
Some...
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...
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...

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

Published on: May 26, 2011

Structure of the integrin alphaIIb transmembrane segment.

Tong-Lay Lau1, Varun Dua, Tobias S Ulmer

  • 1Department of Biochemistry and Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA.

The Journal of Biological Chemistry
|April 18, 2008
PubMed
Summary

Integrin alpha and beta subunits transmit signals across cell membranes. The alphaIIb subunit

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Area of Science:

  • Cell biology
  • Structural biology
  • Biochemistry

Background:

  • Integrins are crucial cell-adhesion receptors involved in bidirectional transmembrane signaling.
  • These receptors utilize single-pass transmembrane segments of alpha and beta subunits to mediate signaling.
  • Understanding the structural dynamics within the membrane is key to integrin function.

Purpose of the Study:

  • To elucidate the structural organization of the alphaIIb transmembrane segment.
  • To compare the structure of the alphaIIb transmembrane segment with that of the beta3 subunit.
  • To establish a structural basis for integrin transmembrane signaling.

Main Methods:

  • Analysis of the alphaIIb transmembrane segment structure using high-resolution techniques.
  • Sequence alignment of conserved residues across human integrin alpha subunits.
  • Comparative structural analysis with the beta3 transmembrane segment.

Main Results:

  • The alphaIIb transmembrane segment features a 24-residue alpha-helix followed by a backbone reversal.
  • This structural motif packs specific phenylalanine residues against the transmembrane helix.
  • Unlike the beta3 subunit, the alphaIIb helix length suggests minimal tilt, and the Gly-Phe-Phe motif is conserved across human alpha integrins.

Conclusions:

  • The alphaIIb transmembrane segment possesses a complex structure beyond a simple helix.
  • This unique structural motif is likely conserved across all integrin alpha subunits.
  • The findings provide a structural foundation for understanding integrin-mediated signaling and rearrangements upon subunit association.