Translocation of Inserted Foreign Epitopes by a Channel-Forming Protein

Certain bacterial protein toxins are able to insert themselves into, and at least partially across, lipid bilayer membranes in the absence of any auxiliary proteins, by using unknown mechanisms to overcome the high energy barrier presented by the hydrophobic bilayer core. We have previously shown th...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1998-04, Vol.95 (8), p.4321-4326
Main Authors: Jakes, Karen S., Kienker, Paul K., Slatin, Stephen L., Finkelstein, Alan
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Amino acids
Antibodies
Bacteria
Base Sequence
Biochemistry
Colicins - chemistry
Colicins - genetics
Colicins - metabolism
Electric potential
Epitopes
Escherichia coli - metabolism
Hemagglutinins
Ion Channels - chemistry
Lipid Bilayers
Molecular Sequence Data
Molecules
Mutagenesis, Insertional - methods
Oligodeoxyribonucleotides
Oligonucleotides
Oligopeptides
P branes
Peptides
Protein transport
Proteins
Recombinant Proteins - chemistry
Recombinant Proteins - metabolism
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Summary:Certain bacterial protein toxins are able to insert themselves into, and at least partially across, lipid bilayer membranes in the absence of any auxiliary proteins, by using unknown mechanisms to overcome the high energy barrier presented by the hydrophobic bilayer core. We have previously shown that one such toxin, colicin Ia, translocates a large, hydrophilic part of itself completely across a lipid bilayer in conjunction with the formation of an ion-conducting channel. To address the question of whether the colicin can translocate any arbitrary amino acid sequence, we have altered the translocated segment by inserting, singly, two different foreign epitopes. Colicins containing either epitope retain significant bactericidal activity and form channels of normal conductance in planar bilayers. Furthermore, anti-bodies added on the side of the bilayer opposite that to which the colicin was added interact specifically with the corresponding epitopes, producing an inhibition of channel closing. Thus, the inserted epitopes are translocated along with the rest of the segment, suggesting that a surprisingly small part of colicin Ia, located elsewhere in the molecule, acts as a nonspecific protein translocator.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.95.8.4321