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Updated: Mar 16, 2026

Isolation of Physiologically Active Thylakoids and Their Use in Energy-Dependent Protein Transport Assays
Published on: September 28, 2018
Cotranslational signal-independent SRP preloading during membrane targeting
Signal recognition particle (SRP) binds secretory proteins before their targeting signals are fully translated, aided by mRNA elements. This mechanism ensures accurate cotranslational membrane targeting, even with limited polypeptide information.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Ribosome-associated factors decode nascent polypeptides for correct cellular fate.
- Accurate recognition of nascent chains by competing factors near the ribosomal exit site remains unclear.
- The signal recognition particle (SRP) targets proteins to the endoplasmic reticulum but its selection mechanism is not fully understood.
Purpose of the Study:
- Investigate the cotranslational membrane-targeting cycle in vivo.
- Understand how the signal recognition particle (SRP) selects its substrates.
- Clarify the role of nascent chain information and mRNA elements in SRP-substrate selection.
Main Methods:
- Ribosome profiling in yeast cells.
- Biochemical fractionation of ribosome populations.
- Analysis of cotranslational nascent chain recognition.
Main Results:
- SRP preferentially binds secretory ribosome-nascent chain complexes (RNCs) before signal translation.
- Non-coding mRNA elements can promote signal-independent SRP pre-recruitment.
- Defined the kinetic interplay between elongation, polypeptide determinants, and mRNA in SRP selection.
Conclusions:
- SRP-mediated cotranslational targeting involves pre-recruitment independent of full signal sequence translation.
- mRNA elements play a role in modulating SRP selection.
- This study elucidates a key mechanism for accurate protein targeting to membranes.
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