Viomycin and Capreomycin (a group of nonribosomal peptide antibiotics) belong to the tuberactinomycin (an essential component in the drug cocktail currently used to fight infections of Mycobacterium tuberculosis) Are among the most effective antibiotics against multidrug-resistant tuberculosis. Viomycin was the first member of the tuberactinomycins to be isolated and identified and was used to treat TB until it was replaced by the less toxic, but structurally related compound, Capreomycin. The tuberactinomycins target bacterial ribosomes, binding RNA and disrupting bacterial protein biosynthesis.
Now Dr. Steitz and his colleagues at Yale's Department of Molecular Biophysics and Biochemistry, have identified two structures of tuberactinomycins bound to the ribosome. The researchers claims that, the identification of these structures provides an insight for the design of novel antibiotic derivatives that could be effective against a variety of drug resistant microorganisms.
As per the claim by Dr.Steitz, both antibiotics (Viomycin and Capreomycin) bind to the same site on the ribosome, which lies at the interface between helix 44 of the small ribosomal subunit and helix 69 of the large ribosomal subunit. The structures of these complexes suggest that the tuberactinomycins inhibit translocation by stabilizing the tRNA in the A site in the pretranslocation state. In addition, these structures show that the tuberactinomycins bind adjacent to the binding sites for the paromomycin and hygromycin B antibiotics, which may enable the development of new derivatives of tuberactinomycins that are effective against drug-resistant strains. The authors have presented two crystal structures of the 70S ribosome in complex with three tRNAs and bound to either viomycin or capreomycin at 3.3-and 3.5-Å resolution, respectively in "Nature Structural & Molecular Biology 14 February 2010 ".
Interestingly, Dr. Steitz was awarded the 2009 Nobel Prize in Chemistry for his groundbreaking work determining a high resolution crystal structure of the 50S subunit of the ribosome which has proved to be a major target for antibiotic development.
Hope this discovery will lead to a new insight for design of novel antibiotic derivatives that could be effective against a variety of drug-resistant microorganisms ....
Ref: http://www.rib-x.com/news_and_events/release_2010_02_16
