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Related Concept Videos

Membrane Asymmetry Regulating Transporters01:19

Membrane Asymmetry Regulating Transporters

Enzymes like flippase, floppase, and scramblase transfer phospholipids from one layer to another in the membrane, thereby affecting membrane asymmetry.
Flippase
Eukaryotic flippases are type-IV P-type ATPases or P4-ATPases belonging to P-type ATPase family proteins that are membrane-bound pumps involved in the ATP-mediated transport of ions and molecules across the membrane. Flippases flip specific phospholipids from the outer to the inner leaflet of a membrane. All P4-ATPases have one...
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Membrane fluidity is explained by the fluid mosaic model of the cell membrane, which describes the plasma membrane structure as a mosaic of components—including phospholipids, cholesterol, proteins, and carbohydrates—that gives the membrane a fluid character.
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Scientists identified the plasma membrane in the 1890s and its principal chemical components (lipids and proteins) by 1915. The model for plasma membrane structure, proposed in 1935 by Hugh Davson and James Danielli, was the first model to be widely accepted in the scientific community. The model was based on the plasma membrane's "railroad track" appearance in early electron micrographs. Davson and Danielli theorized that the plasma membrane's structure resembled a sandwich with the analogy of...
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The fluid mosaic model was first proposed as a visual representation of research observations. The model comprises the composition and dynamics of membranes and serves as a foundation for future membrane-related studies. The model depicts the structure of the plasma membrane with a variety of components, which include phospholipids, proteins, and carbohydrates. These integral molecules are loosely bound, defining the cell’s border and providing fluidity for optimal function.

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A Fluorescence-based Assay of Phospholipid Scramblase Activity
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Published on: September 20, 2016

Structural properties of model phosphatidylcholine flippases.

Marcella Langer1, Rashmi Sah, Anika Veser

  • 1Lehrstuhl für Chemie der Biopolymere, Department für biowissenschaftliche Grundlagen, Technische Universität München, Weihenstephaner Berg 3, 85354 Freising and Munich Center For Integrated Protein Science (CIPS(M)), Germany.

Chemistry & Biology
|January 29, 2013
PubMed
Summary

Newly synthesized lipids flip between membrane layers, a process crucial for cell growth. Researchers found that transmembrane peptides and SNARE proteins can act as lipid flippases, influencing lipid distribution.

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Area of Science:

  • Biochemistry
  • Membrane Biology
  • Molecular Biophysics

Background:

  • Lipid translocation (flip-flop) across lipid bilayers is essential for membrane biogenesis and phospholipid distribution.
  • A specific enzyme (flippase) responsible for this biogenic lipid transport has not been identified.

Purpose of the Study:

  • To investigate the biophysical mechanisms underlying lipid flip-flop mediated by transmembrane peptides.
  • To determine the role of peptide structure and membrane environment in regulating lipid translocation efficiency.
  • To explore the potential of SNARE proteins as endogenous lipid flippases.

Main Methods:

  • Utilized model transmembrane peptides with varying helix-destabilizing residues and flanking charge states.
  • Assessed lipid flip-flop efficiency using reporter lipids with different headgroups (phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine).
  • Investigated the impact of host membrane composition on peptide-mediated lipid translocation.
  • Examined the lipid flippase activity of recombinant SNARE proteins.

Main Results:

  • Transmembrane peptide efficiency in lipid flipping is significantly influenced by helix dynamics, residue content, flanking charge, and membrane composition.
  • Increased backbone dynamics in transmembrane helices correlated with enhanced flipping of phosphatidylcholine and phosphatidylserine lipids.
  • More rigid helices preferentially facilitated phosphatidylethanolamine lipid flipping.
  • Recombinant SNARE proteins demonstrated notable lipid flippase activity, sharing structural features with effective model peptides.

Conclusions:

  • Transmembrane peptide structure and dynamics are critical determinants of lipid translocation efficiency.
  • SNARE proteins possess intrinsic lipid flippase activity, suggesting a role in membrane lipid homeostasis.
  • This work identifies potential mechanisms and candidates for biogenic lipid transport across membranes.