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Related Concept Videos

Protein Diffusion in the Membrane01:24

Protein Diffusion in the Membrane

Proteins show rotational as well as lateral diffusion across the membrane. The lateral diffusion of proteins was confirmed through the cell fusion experiment where mouse and human cells were fused, resulting in hybrid cells. When the human and mouse cells fused, the specific membrane proteins on human and mouse cells were marked with the red and green-fluorescent markers, respectively. Initially, the red and green fluorescence was located on the respective hemisphere of the cell. As time...
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Lipopolysaccharides (LPS) are crucial components of the outer membrane of Gram-negative bacteria, serving both structural and functional roles. It contributes to membrane stability and protects bacteria from host immune responses. LPS is composed of three major regions—lipid A, a core oligosaccharide, and an O antigen. The biosynthesis and assembly of LPS involve a highly coordinated set of enzymatic reactions and transport mechanisms. Additionally, LPS is recognized as an endotoxin, triggering...
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Bacterial Translocation and Protein Secretion

Bacterial protein secretion involves translocation systems to ensure proteins reach their designated locations, including the plasma membrane, periplasm, outer membrane, or the external environment. These translocation systems are vital for bacterial physiology, supporting processes like membrane assembly, enzymatic activity in the periplasm, and interactions with the external environment. The division of labor between Sec and Tat pathways ensures efficiency in handling proteins with diverse...
Diffusion01:12

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Diffusion is the passive movement of substances down their concentration gradients—requiring no expenditure of cellular energy. Substances, such as molecules or ions, diffuse from an area of high concentration to an area of low concentration in the cytosol or across membranes. Eventually, the concentration will even out, with the substance moving randomly but causing no net change in concentration. Such a state is called dynamic equilibrium, which is essential for maintaining overall...
Diffusion01:21

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Diffusion is a type of passive transport. In passive transport, a substance tends to move from an area of high concentration to an area of low concentration until the concentration is equal across the space. For example, take the diffusion of substances through the air. When someone opens a perfume bottle in a room filled with people, the perfume is at its highest concentration in the bottle and is at its lowest at the edges of the room. The perfume vapor will diffuse, or spread away, from the...
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Passive diffusion is a critical process that allows small lipophilic drugs to cross the cell membrane along a concentration gradient. This mechanism's efficiency depends on four primary factors: the membrane's surface area, the drug's lipid-water partition coefficient, the concentration gradient, and the membrane's thickness.
When administered orally, drugs establish a substantial concentration gradient between the gastrointestinal (GI) lumen and the bloodstream, expediting their diffusion into...

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Separation of the Cell Envelope for Gram-negative Bacteria into Inner and Outer Membrane Fractions with Technical Adjustments for Acinetobacter baumannii
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Ligand-gated diffusion across the bacterial outer membrane.

Bryan W Lepore1, Mridhu Indic, Hannah Pham

  • 1University of Massachusetts Medical School, Program in Molecular Medicine, 373 Plantation Street, Worcester, MA 01605, USA.

Proceedings of the National Academy of Sciences of the United States of America
|May 20, 2011
PubMed
Summary

Researchers discovered ligand gating in the outer membrane of Gram-negative bacteria. The long-chain fatty acid transporter FadL (Fatty acid transport protein) in Escherichia coli opens a channel upon substrate binding.

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Area of Science:

  • Membrane protein structure and function
  • Gram-negative bacterial outer membrane transport
  • Ligand-gated channel mechanisms

Background:

  • Ligand-gated channels are crucial for cellular transport in many organisms.
  • Outer membranes of Gram-negative bacteria lack known ligand-gated channels.
  • Long-chain fatty acid transport is essential for bacterial physiology.

Purpose of the Study:

  • To investigate the mechanism of the outer membrane long-chain fatty acid transporter (FadL) from Escherichia coli.
  • To determine if ligand binding induces conformational changes in FadL.
  • To identify novel ligand-gated transport mechanisms in bacterial outer membranes.

Main Methods:

  • In vivo transport assays to measure substrate uptake.
  • Intrinsic tryptophan fluorescence to detect conformational changes.
  • X-ray crystallography to determine high-resolution protein structure.

Main Results:

  • High-affinity substrate binding to FadL triggers conformational changes.
  • These changes occur at the N-terminus of the protein.
  • The conformational changes result in the opening of a channel for substrate diffusion.

Conclusions:

  • Escherichia coli FadL represents a unique model for diffusion-driven transport in the outer membrane.
  • Ligand gating within this beta-barrel protein is essential for channel formation.
  • This finding reveals a novel mechanism for transport across the bacterial outer membrane.