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Fingerloop activates cargo delivery and unloading during cotranslational protein targeting
Aileen R Ariosa1, Stacy S Duncan, Ishu Saraogi
1Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
Molecular Biology of the Cell
|November 9, 2012
Summary
The signal recognition particle's (SRP) fingerloop is crucial for protein targeting. It activates SRP, enhancing cargo delivery to membranes by facilitating interactions with the SRP receptor (SR).
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- The signal recognition particle (SRP) pathway mediates cotranslational protein targeting to membranes.
- Effective communication between SRP's M and GTPase domains is essential for initiating SRP receptor (SR) interaction.
- The role of the conserved fingerloop in SRP's M domain has been unclear.
Purpose of the Study:
- To elucidate the function of the SRP fingerloop in the protein targeting pathway.
- To understand how signal sequence binding is communicated within SRP to activate downstream events.
Main Methods:
- Biochemical assays to assess SRP function.
- Structural analysis of SRP and its interactions.
- Mutational studies of the fingerloop region.
Main Results:
- The fingerloop is essential for inducing an active SRP conformation.
- It promotes efficient SRP receptor (SR) recruitment and GTPase activation.
- The fingerloop significantly enhances cargo unloading onto the target membrane.
Conclusions:
- The fingerloop acts as the primary sensor for signal sequence binding in SRP.
- It transmits binding information to the M-G domain linker, activating the SRP-SR complex.
- This mechanism ensures efficient and timely protein delivery to cellular membranes.
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