Related Experiment Video
Updated: Feb 10, 2026
12:27
Measuring Peptide Translocation into Large Unilamellar Vesicles
Published on: January 27, 2012
14.3K
Measuring Endoplasmic Reticulum Signal Sequences Translocation Efficiency Using the Xbp1 Arrest Peptide
Theresa Kriegler1, Anastasia Magoulopoulou1, Rocio Amate Marchal1
1Department of Biochemistry and Biophysics, Arrhenius Laboratories of Natural Sciences, Stockholm University, Svante Arrhenius väg 16C, Stockholm 10691, Sweden.
Cell Chemical Biology
|May 15, 2018
Summary
The study reveals how signal sequences guide secretory proteins into the endoplasmic reticulum (ER). Efficient signals pull nascent chains through the ER membrane, while inefficient ones show weaker engagement with the translocation machinery.
Area of Science:
- Molecular Biology
- Cell Biology
- Protein Trafficking
Background:
- Secretory proteins cross the mammalian endoplasmic reticulum (ER) membrane co-translationally.
- This translocation is mediated by the ribosome-sec61 translocation machinery.
- Signal sequences, diverse in properties, are thought to dominate ER targeting and translocation.
Purpose of the Study:
- To analyze co-translational events for secretory proteins with varying signal sequence efficiencies.
- To functionally measure the efficiency of ER signal sequences.
- To investigate the role of signal sequence properties in co-translational translocation.
Main Methods:
- Utilized an assay based on Xbp1 peptide-mediated translational arrest.
- Compared co-translational events for proteins with efficient versus inefficient signal sequences.
- Measured the functional efficiency of ER signal sequences.
Main Results:
- Efficient signal sequences induce a two-phase translocation event, pulling the nascent chain from the ribosome.
- This pulling resumes translation, leading to full-length product formation.
- Inefficient signal sequences exhibit a single, weaker pulling event, indicating suboptimal engagement with the translocation machinery.
Conclusions:
- Signal sequence efficiency significantly impacts the dynamics of co-translational translocation.
- Marginally hydrophobic signal sequences may inadequately engage the ER translocation machinery.
- The study provides insights into the functional mechanism of signal sequences in protein targeting.
Related Concept Videos
01:39Endoplasmic Reticulum
110.5K
The Endoplasmic Reticulum (ER) in eukaryotic cells is a substantial network of interconnected membranes with diverse functions, from calcium storage to biomolecule synthesis. A primary component of the endomembrane system, the ER manufactures phospholipids critical for membrane function throughout the cell. Additionally, the two distinct regions of the ER specialize in the manufacture of specific lipids and proteins.
110.5K
01:43The Endoplasmic Reticulum
21.7K
The endoplasmic reticulum or ER makes up for more than half of the membranes in a cell and accounts for 10% of total cell volume. It is also the primary protein and lipid synthesis factory for most cell organelles, such as the Golgi apparatus, lysosomes, secretory vesicles, and the plasma membrane. Despite being the most extensive and functionally complex subcellular organelle, ER was the last to be discovered. After years of deliberation, Keith Porter and George Palade in the year 1954,...
21.7K
01:21Smooth Endoplasmic Reticulum
8.2K
Smooth endoplasmic reticulum or smooth ER is a sub-organelle with specialized functions in animal cells and plant cells. It is often associated with the tubule morphology of the endoplasmic reticulum.
The ER provides optimal conditions for synthesizing steroid hormones and lipids, such as phospholipids and triglycerides. Traditionally, lipid metabolism was considered to be a smooth ER function. However, there is no direct evidence to prove that rough ER is completely excluded from lipid...
The ER provides optimal conditions for synthesizing steroid hormones and lipids, such as phospholipids and triglycerides. Traditionally, lipid metabolism was considered to be a smooth ER function. However, there is no direct evidence to prove that rough ER is completely excluded from lipid...
8.2K
01:34Directing Proteins to the Rough Endoplasmic Reticulum
17.8K
The organelle-specific signaling sequences direct proteins synthesized in the cytosol to their final destination like ER, mitochondria, peroxisomes, etc. Some of the proteins directed to ER are then trafficked via vesicles to other organelles within the cell or the extracellular environment through the Golgi complex. For example, the rough ER synthesizes soluble proteins for transportation to the lysosomes or secretion out of the cell. It can also synthesize transmembrane proteins that can...
17.8K
01:19Contact-dependent Signaling
47.6K
Contact-dependent signaling, as the name suggests, requires that communicating cells be in direct contact with each other. This is achieved either through receptor-ligand interactions or by specialized cytoplasmic channels that allow the flow of small molecules between cells. In animal cells, channels called gap junctions facilitate contact-dependent signaling in certain tissues, whereas, plasmodesmata perform a similar function in plants.
Gap Junctions
In animal cells, gap junctions are formed...
Gap Junctions
In animal cells, gap junctions are formed...
47.6K
01:41Signal Sequences and Sorting Receptors
15.5K
Signal sequences are short amino acid sequences that guide newly synthesized proteins to their proper location within the cell. Classical signal sequences are fifteen to sixty amino acids long and present at the N-terminus of a polypeptide chain. Each signal sequence has a conserved segment of basic residues towards their N terminus, a hydrophobic core, and a C-terminus rich in polar residues. The C-terminus also contains a signal cleavage site and features a -3 -1 sequence motif. The -3-1...
15.5K