Related Experiment Video
Updated: May 13, 2026
06:55
Polarized Translocation of Fluorescent Proteins in Xenopus Ectoderm in Response to Wnt Signaling
Published on: May 26, 2011
Densin-180 is not a transmembrane protein
Dai-Chi Liu1, Guey-Mei Jow, Chau-Chin Chuang
1Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
Cell Biochemistry and Biophysics
|March 22, 2013
Summary
Densin-180, a key post-synaptic density protein, is not a transmembrane protein. New evidence shows densin associates with the cell membrane, challenging previous models and clarifying its synaptic structure.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Densin-180 (densin) is a major component of the post-synaptic density (PSD) in excitatory synapses.
- Its role in synaptic regulation is suggested by interactions with other post-synaptic proteins.
- Previous studies proposed conflicting models for densin's structure: transmembrane protein versus membrane-associated protein.
Purpose of the Study:
- To investigate the structural topology of densin-180.
- To determine if densin possesses an extracellular domain.
- To clarify densin's interaction with the cell membrane.
Main Methods:
- Immunofluorescence using extracellularly applied antibodies to test epitope accessibility.
- Protease digestion assays.
- Surface biotinylation experiments.
- Protein extraction to assess hydrophobic interactions with the cell membrane.
Main Results:
- No tested densin epitopes were accessible to extracellular antibodies.
- Protease digestion and surface biotinylation failed to confirm an extracellular domain.
- Protein extraction revealed significant hydrophobic interaction with the cell membrane, inconsistent with cytosolic proteins.
Conclusions:
- The data do not support a transmembrane model for densin-180.
- Findings are consistent with densin being a membrane-associated protein.
- This clarifies densin's topology and its role in synaptic structure.
Related Concept Videos
01:25Single-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...
01:26Insertion 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...
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...
01:29Insertion 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...
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...
03:18Non-LTR Retrotransposons
As the name suggests, non-LTR retrotransposons lack the long terminal repeats characteristic of the LTR retrotransposons. Additionally, both LTR and non-LTR retrotransposons use distinct mechanisms of mobilization. Non-LTR retrotransposons are further divided into two classes - Long interspersed nuclear elements (LINEs) and short interspersed nuclear elements (SINEs), both of which occur abundantly in most mammals, including humans. Some of the active non-LTR retrotransposons in humans are L1...
01:09Multi-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...
α-Helix containing multi-pass transmembrane proteins
Multi-pass transmembrane proteins such as G-protein-linked receptors (GPCRs) and...
01:28Protein 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.
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.