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Related Experiment Video

Updated: Jun 13, 2026

Quantitative Immunofluorescence to Measure Global Localized Translation

Quantitative Immunofluorescence to Measure Global Localized Translation

Published on: August 22, 2017

Sequential checkpoints govern substrate selection during cotranslational protein targeting.

Xin Zhang¹, Rumana Rashid, Kai Wang

¹Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.

Science (New York, N.Y.)

|May 8, 2010

Summary

High fidelity protein targeting in bacteria relies on multiple checkpoints, not just initial binding. The signal recognition particle (SRP) pathway ensures correct protein delivery through sequential selection steps.

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Area of Science:

Molecular Biology
Cell Biology
Biophysics

Background:

Accurate protein localization is crucial for cellular function.
The precise mechanisms ensuring high fidelity in protein targeting pathways remain largely unknown.
The signal recognition particle (SRP) pathway in E. coli targets proteins to the bacterial inner membrane via signal sequences.

Purpose of the Study:

To investigate the mechanisms underlying high fidelity in the bacterial SRP pathway.
To determine how the SRP pathway achieves precise selection of cargo proteins.

Main Methods:

Utilized biophysical assays to study protein-cargo interactions.
Analyzed the sequential steps of the SRP targeting pathway in Escherichia coli.

Main Results:

High fidelity is not solely dependent on the initial binding affinity of SRP to cargo.
Incorrect cargo proteins are rejected through multiple checkpoints during the targeting process.
These checkpoints act cumulatively to ensure accurate protein localization.

Conclusions:

High fidelity substrate selection in the SRP pathway results from a series of checkpoints.
This multi-checkpoint principle may be broadly applicable to other selective signal recognition pathways.
Understanding these mechanisms is key to comprehending fundamental cellular processes.