Researchers solve first structure of a key to intact DNA i...( HOUSTON - Researchers have solved th...),Health

HOUSTON - Researchers have solved the structure of a DNA-protein complex that is crucial in the spread of antibiotic resistance among bacteria. Knowing this structure also provides fundamental insight into how cells successfully divide into two new cells with intact DNA

The report in the Dec. 20th issue of Nature focuses on how DNA separates and maintains its integrity when a cell divides. Using X-ray crystallography, the team led by structural biologists at The University of Texas M. D. Anderson, with colleagues at the University of Sydney, Australia, produced clear 3-D images of the structure that results when two proteins connect with a DNA site to "segregate" DNA during cell division.

"We solve structures to answer questions about how molecules carry out their biological functions. Without knowing the structure, you can't understand molecular mechanisms at a detailed level," says lead author Maria Schumacher, Ph.D., associate professor in M. D. Anderson's Department of Biochemistry and Molecular Biology.

In this case, Schumacher and colleagues answer a basic science question and flag a possible target for clinical attack on antibiotic-resistant Staphlococcus Aureas, a tenacious and often lethal staph infection.

"The plasmid segregation system we are working on, called pSK41, is found in S. aureus and confers resistance to multiple antibiotics, including the drug of last resort, vancomycin," Schumacher says. "Because the segregation systems are essential for the retention of these multidrug resistant plasmids, they represent wonderful drug targets."

Plasmids are additional strips or circles of DNA found in bacteria that provide the bacterium with some mechanism of defense - in this case, protection against antibiotics. Plasmids can be transferred from one type of bacteria to another through a number of mechanisms.

Plasmids are also a great model for understanding cell division and segregation, Schuma
'/>"/>