X-rays pinpoint drug target for bacteria that affect hundreds of millions worldwide
Experiments at the U.S. Department of Energy's (DOE) SLAC National Accelerator Laboratory have revealed a potential new way to attack common stomach bacteria that cause ulcers and significantly increase the odds of developing stomach cancer.
The breakthrough, made using powerful X-rays from SLAC's Stanford Synchrotron Radiation Lightsource (SSRL), was the culmination of five years of research into the bacterium Helicobacter pylori, which is so tough it can live in strong stomach acid. At least half the world's population carries H. pylori and hundreds of millions suffer health problems as a result; current treatments require a complicated regimen of stomach-acid inhibitors and antibiotics.
"We were looking for a means to disrupt H. pylori's own mechanism for protecting itself against stomach acid," said Hartmut "Hudel" Luecke, a researcher at the University of California, Irvine, and principal investigator on the paper, published online Dec. 9 in Nature. With this study, he said, "We have deciphered the three-dimensional molecular structure of a very promising drug target."
Luecke and his team zeroed in on tiny channels that H. pylori uses to allow in urea from gastric juice in the stomach; it then breaks this compound into ammonia, which neutralizes stomach acid. Blocking the channels would disable this protective system, leading to a new treatment for people with the infection.
Solving the structure of the protein to find the specific area to target wasn't easy. The channels are formed by the protein embedded in the bacterium's cell membrane, and membrane proteins are notoriously difficult to crystallize, which is a prerequisite for using protein crystallography, the main technique for determining protein structures. This technique bounces X-rays off of the electrons in the crystallized protein to generate the experimental data used to build a 3-D map showing how the protein's atoms are arranged.