Related Experiment Video
Updated: Jan 2, 2026

Characterization of Membrane Transporters by Heterologous Expression in E. coli and Production of Membrane Vesicles
Published on: December 31, 2019
Delivery of mirror image polypeptides into cells
Amy E Rabideau1, Xiaoli Liao1, Bradley L Pentelute1
1Department of Chemistry , Massachusetts Institute of Technology , 77 Massachusetts Ave. 18-596 , Cambridge , MA 02139 , USA .
Mirror image peptides can now enter cells using anthrax toxin components. This new method allows for higher concentrations of d-peptide conjugates inside cells for therapeutic applications.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Mirror image peptides exhibit unique stability and immunogenicity, but their intracellular applications are limited by delivery challenges.
- Cellular uptake of mirror image biopolymers is difficult due to membrane transport barriers.
Purpose of the Study:
- To investigate the intracellular delivery of mirror image peptides and proteins using the anthrax toxin protective antigen (PA) and lethal factor (LFN) system.
- To evaluate the stability and concentration of delivered mirror image peptides within the cell cytosol.
Main Methods:
- Conjugating mirror image polypeptide cargo to the C-terminus of the PA-binding domain of LFN.
- Utilizing the PA/LFN system for translocation into the cytosol of mammalian cells.
- Employing Western blot analysis to determine steady-state concentrations of delivered peptides.
Main Results:
- Mirror image polypeptides and proteins were efficiently translocated into cells, comparable to their natural L-enantiomers.
- d-peptide conjugates at the C-terminus of LFN achieved higher steady-state concentrations in the cytosol than l-peptide conjugates.
- Demonstrated successful delivery of a d-peptide MDM2 antagonist to disrupt the p53/MDM2 interaction in cancer cells.
Conclusions:
- The PA/LFN system provides an adaptable platform for the intracellular delivery of mirror image peptides and proteins.
- This method overcomes previous limitations in exploring the intracellular functions of mirror image biopolymers.
- The enhanced intracellular stability and concentration of d-peptides offer new therapeutic possibilities, particularly in cancer treatment.
More Related Videos
10:30Delivery of Proteins, Peptides or Cell-impermeable Small Molecules into Live Cells by Incubation with the Endosomolytic Reagent dfTAT
Published on: September 2, 2015
11:24Direct Protein Delivery to Mammalian Cells Using Cell-permeable Cys2-His2 Zinc-finger Domains
Published on: March 25, 2015
Related Concept Videos
Insertion of Single-pass Transmembrane Proteins in the RER
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
Post-translational Translocation of Proteins to the RER
Targeting proteins to the ER
Hsp40 and Hsp70 chaperone molecules bind the translated proteins in the cytosol to prevent their folding. The chaperone binding helps to keep the signal...
Cotranslational Protein Translocation
Sec61 channel partners for cotranslational translocation
During cotranslational translocation, the Sec61 channel partners with the signal recognition particle (SRP), the signal recognition particle receptor (SR), and the ribosomes to transport the nascent polypeptide chain...
Insertion of Multi-pass Transmembrane Proteins in the RER
The multipass transmembrane proteins are the type IV integral membrane proteins with multiple topogenic sequences determining their spatial arrangement in the ER membrane. Nearly all multipass proteins lack a cleavable signal sequence and use...
Translocation of Proteins into the Mitochondria
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Directing Proteins to the Rough Endoplasmic Reticulum