Interactions between the toxin Kid of the bacterial parD system and the antitoxins Kis and MazE

The proteins Kid and Kis are the toxin and antitoxin, respectively, encoded by the parD operon of Escherichia coli plasmid R1. Kis prevents the inhibition of E. coli cell growth caused by the RNA cleavage activity of Kid. Overproduction of MazE, the chromosome‐encoded homologue of Kis, has been demo...

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Published in:Proteins, structure, function, and bioinformatics structure, function, and bioinformatics, 2007-04, Vol.67 (1), p.219-231
Main Authors: Kamphuis, Monique B., Monti, Maria Chiara, van den Heuvel, Robert H. H., Santos-Sierra, Sandra, Folkers, Gert E., Lemonnier, Marc, Díaz-Orejas, Ramón, Heck, Albert J. R., Boelens, Rolf
Format: Article
Language:English
Subjects:
Antitoxins
Bacterial Proteins - chemistry
Bacterial Proteins - metabolism
Bacterial Toxins - chemistry
Bacterial Toxins - metabolism
DNA-Binding Proteins - chemistry
DNA-Binding Proteins - genetics
DNA-Binding Proteins - metabolism
Escherichia coli - genetics
Escherichia coli Proteins - chemistry
Escherichia coli Proteins - genetics
Escherichia coli Proteins - metabolism
native macromolecular mass spectrometry
NMR spectroscopy
Nuclear Magnetic Resonance, Biomolecular
oligomerization
Operon
plasmid maintenance
plasmid maintenance, protein–protein interactions
Plasmids - genetics
protein-protein interactions
Structure-Activity Relationship
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Summary:The proteins Kid and Kis are the toxin and antitoxin, respectively, encoded by the parD operon of Escherichia coli plasmid R1. Kis prevents the inhibition of E. coli cell growth caused by the RNA cleavage activity of Kid. Overproduction of MazE, the chromosome‐encoded homologue of Kis, has been demonstrated to neutralize Kid toxicity to a certain extent in the absence of native Kis. Here, we show that a high structural similarity exists between these antitoxins, using NMR spectroscopy. We report about the interactions between Kid and Kis that are responsible for neutralization of Kid toxicity and enhance autoregulation of parD transcription. Native macromolecular mass spectrometry data demonstrate that Kid and Kis form multiple complexes. At Kis:Kid ratios equal to or exceeding 1:1, as found in vivo in a plasmid‐containing cell, various complexes are present, ranging from Kid2–Kis2 tetramer up to Kis2–Kid2–Kis2–Kid2–Kis2 decamer. When Kid is in excess of Kis, corresponding to an in vivo situation immediately after loss of the plasmid, the Kid2–Kis2–Kid2 heterohexamer is the most abundant species. NMR chemical shift and intensity perturbations in the 1H 15N HSQC spectra of Kid and Kis, observed when titrating the partner protein, show that the interaction sites of Kid and Kis resemble those within the previously reported MazF2–MazE2–MazF2 complex. Furthermore, we demonstrate that Kid2–MazE2 tetramers can be formed via weak interactions involving a limited part of the Kis‐binding residues of Kid. The functional roles of the identified Kid–Kis and Kid–MazE interaction sites and complexes in toxin neutralization and repression of transcription are discussed. Proteins 2007; © 2007 Wiley‐Liss, Inc.
ISSN:0887-3585
1097-0134
DOI:10.1002/prot.21254