A method that cells use to communicate and coordinate activities has been confirmed by researchers from Cornell University, Monsanto Co. and Argonne.
This work could lead to new drugs to fight such diseases as cystic fibrosis and the bubonic plague, or to new technologies that perform useful environmental tasks, such as filtering water.
Biologists have theorized that bacteria communicate by releasing and sensing chemical pheromones to detect their population densities. This activity is termed "quorum sensing."
Using Argonne's
Structural Biology Center (SBC), the researchers confirmed this theory. They determined the molecular structure of a key protein - TraR - in this interbacterial communication
and witnessed how TraR acts as a relay to sense pheromones and then activate genes to create biofilms. A common example of a biofilm is the scum found on ponds.
More than 70 types of organisms are believed to use this molecular "census-taking" process including Yersinia pestis - the bubonic plague bacterium.
"We believe the quorum-sensing process signals bacteria to create biofilms - mats of bacterial cells over a solid surface," said Argonne biophysicist Rong-guang Zhang.
Zhang is lead author of an article describing their results in the June 27 issue of Nature.
"To see how these cells communicate, we crystallized and studied the structure of the TraR protein complexed with pheromone and DNA of the well-known Agrobacterium tumefaciens,
an agricultural pathogen that causes tumors in plants," said Zhang.
Researchers got a microsecond snapshot of quorum sensing in progress.
Knowing the structure of this important quorum-sensing protein may permit researchers to treat bacterial biofilm-related diseases, such as cystic fibrosis, by creating drugs to block the chemical signals that form biofilms.
Conversely, scientists could stimulate the formation of useful biofilms to filter water or perform other useful environmental tasks.
The structural information comes from shining X-rays from the Advanced Photon Source – the nation's most brilliant source of X-rays – onto tiny, frozen protein crystals.
The X-ray images are captured by a quick, electronic camera. Advanced software converts the data into 3-D images biologists use to infer how these proteins work and interact with other molecules.
"The structure," Zhang said, "is the most asymmetrical we have seen for a protein-DNA complex. It is shaped liked a butterfly with its wings bent back."
Pheromones lie fully embedded within the protein. To activate the pheromones, several amino acid residues critical to RNA polymerase activation, or gene copying, make contact with the "butterfly body" of TraR. – Evelyn Brown
Xanya Sofra Weiss
No comments:
Post a Comment