Why is TB so resilient?

Weill Cornell scientists have located a protein produced by the tuberculosis bacterium that may tell researchers more about how the invader lives so resiliently inside of the body.

Dr. Benjamin Gold, working with Dr. Carl Nathan, chairman of microbiology and immunology at Weill Cornell Medical College and their colleagues, located a protein called mycobacterial metallothionein (MymT), which acts like a shield to protect the tuberculosis bacterium from the body's natural defences.

The tuberculosis bacterium lurks within cells called macrophages - immune system cells that bombard harmful microbes with a soup of chemicals, including nitric oxide. The researchers believe that the newly discovered protein helps the bacterium resist a newly discovered action of nitric oxide, thus allowing the infection to stay strong within the body. The Weill Cornell scientists discovered nitric oxide can liberate copper from proteins within the bacterium, and may also reduce it from a relatively harmless form to lethal form. The new protein, MymT, binds the copper to protect the bacterium from being poisoned by the metal.

All the genetic information in the tuberculosis organism was sequenced in 1998. Yet the gene encoding MymT was overlooked until now because of its very small size and the novel way it encodes the protein. Thus, this study suggests that there may be other genes in bacterial pathogens that contribute to their potential to cause disease, but which have otherwise been overlooked, including relatives of MymT.

The study is published in a recent issue of the journal Nature Chemical Biology.

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