German researchers have identified a group of new natural antibiotics against tuberculosis. The compounds have been isolated from Myxobacteria, and works by inhibiting the pathogen's RNA polymerase, thus preventing the translation of the bacteria's DNA.

"In our fundus we have three substances - myxopyronin, corallopyronin and ripostatin - which were isolated and characterised chemically and biologically. Already many years ago we recognized their unusual antibiotic effect. It was directed in an unknown manner against the bacterial RNA polymerase, i.e. the enzyme that reads the DNA of the pathogen. In eukaryontic cells, which human cells are also belonging to, the substances do not attack the RNA polymerase."

The results supported the indication that the natural substances block the bacterial RNA polymerase in a new manner: the natural substances append to another location within the RNA polymerase than the antibiotics previously investigated.

They attach to the enzyme - which looks like an open crab claw - directly at its joint position. Subsequently the enzyme is no longer able to open the claw. By this mechanism of action the active substances prevent the RNA polymerase from adhering to the DNA - reading of the genetic materials is suppressed completely. This new mechanism also operates in bacteria that are resistant to conventional antibiotics.

The study has been published in the journal Cell, doi 10.1016/j.cell.2008.09.033.

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