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Updated: Aug 11, 2026

Engineering Cell-permeable Protein
Published on: December 28, 2009
Translocation of inserted foreign epitopes by a channel-forming protein
K S Jakes1, P K Kienker, S L Slatin
1Department of Physiology and Biophysics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA. jakes@aecom.yu.edu
Bacterial toxins like colicin Ia can insert into lipid membranes. This study shows colicin Ia can translocate foreign protein sequences, suggesting a general protein translocation mechanism.
Area of Science:
- Biochemistry
- Molecular Biology
- Membrane Biophysics
Background:
- Bacterial protein toxins can penetrate lipid bilayers via unknown mechanisms.
- Colicin Ia translocates a hydrophilic segment across lipid bilayers, forming ion channels.
Purpose of the Study:
- To investigate if colicin Ia can translocate arbitrary amino acid sequences.
- To determine the mechanism of colicin Ia translocation across lipid bilayers.
Main Methods:
- Insertion of foreign epitopes into the translocated segment of colicin Ia.
- Assessment of bactericidal activity and channel conductance in planar bilayers.
- Antibody-based interaction studies to confirm epitope translocation.
Main Results:
- Colicins with inserted epitopes retained bactericidal activity and normal channel conductance.
- Antibodies specifically interacted with translocated epitopes, inhibiting channel closing.
- Evidence suggests a small, separate part of colicin Ia acts as a general protein translocator.
Conclusions:
- Colicin Ia possesses a general protein translocation capability.
- The mechanism for crossing the hydrophobic lipid core is not sequence-specific.
- A discrete domain within colicin Ia likely mediates nonspecific protein translocation.
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