Characterization of the interaction between the Sec61 translocon complex and ppαF using optical tweezers
Luka Robeson1, Nathalie Casanova-Morales1,2, Francesca Burgos-Bravo1,3
1Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile.
Summary
Researchers quantified the signal peptide (SP) and Sec61 translocon interaction using optical tweezers. Mycolactone, an inhibitor, weakened this essential binding, while SP mutations disrupted it.
Area of Science:
- Cell Biology
- Biophysics
Background:
- The Sec61 translocon facilitates protein translocation into the endoplasmic reticulum.
- Signal peptides (SP) are crucial for targeting proteins to the translocon.
- SP mutations linked to diseases highlight the importance of SP/Sec61 interaction, yet biophysical details are lacking.
Purpose of the Study:
- To biophysically characterize the dissociation kinetics between Sec61 and a signal peptide.
- To investigate the effects of a translocation inhibitor and mutations on this interaction.
Main Methods:
- Utilized optical tweezers force spectroscopy to measure dissociation parameters.
- Applied Dudko-Hummer-Szabo models to analyze rupture force data.
- Examined the impact of mycolactone and a signal peptide mutant.
Main Results:
- Quantified off-rate constant and transition state distance for SP/Sec61 dissociation.
- Mycolactone increased dissociation rates and weakened the SP/Sec61 interaction.
- A translocation-deficient SP mutant exhibited unstable binding, losing specificity.
Conclusions:
- Provided quantitative biophysical characterization of signal peptide/Sec61 dissociation.
- Demonstrated how a translocation inhibitor modifies unbinding parameters.
- Highlighted the role of specific SP sequences in maintaining stable Sec61 interaction.
