Download Structural analysis of the protein complex involved in the

August 19, 2005
Riken Discovery Research Institute
The Cellular Physiology Laboratory
Chief Scientist: Dr. Fumio Hanaoka
Senior Research Scientist: Dr. Katsuhiko Kamada
Structural analysis of the protein complex
involved in the maintenance of plasmid DNA
Researchers at the Cellular Physiology Laboratory (Chief Scientist: Dr. Fumio Hanaoka;
Senior Research Scientist: Dr. Katsuhiko Kamada) have determined the structure of the
protein complex involved in the maintenance of plasmid DNA in bacteria, and elucidated
its molecular mechanisms.
Some eubacteria possess plasmid DNA that has acquired various antibiotic-resistant
genes. The plasmid DNA is maintained in the bacteria by two types of protein, known as
toxin and antitoxin. Researchers have crystallized the free YoeB toxin and the YoeB
(toxin)-YefM (antitoxin) protein complex, which reside in the host organism Escherichia
coli, and determined their structures using beamlines at two light source facilities
(Photon Factory and SPring-8). This analysis revealed that the YefM antitoxin dimer
blocks the RNase activity of YoeB toxin by inducing a conformational change at the
catalytic site of YoeB toxin.
If it is possible to interfere with the binding of antitoxin to toxin, it may be feasible to elicit
RNase activity of the toxin of the bacteria itself or its plasmid DNA, and thereby induce
cell death of the bacteria. The development of novel antibiotics that target the
maintenance mechanism of plasmid DNA in bacteria such as those that cause
nosocomial infections may yield benefits in the treatment of these infections. The
research results were published in the August 19 issue of the U.S. scientific journal
"Molecular Cell".
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