"E. coli is responsible for urinary tract infections, one of the most prevalent diseases in the U.S.," said Brookhaven biologist Huilin Li, the lead researcher on the study, described in the November 2, 2004, online edition of the Journal of Molecular Biology. "Between 50 and 80 percent of U.S. women will experience a urinary tract infection at least once during their lifetimes."
"In the first stage of the infection, E. coli binds tightly to human kidney cells, using an 'adhesive protein' secreted by the cells through a membrane protein 'channel.' Our structure of this protein channel helps show how secretion occurs, which may eventually lead us to determine how to stop E. coli from attaching to the human cell," said Li.
The protein channel, known as "PapC," is a member of the "chaperone/usher" family, channels that not only provide a pathway for certain substances to leave a cell but also participate in preparing the substance for secretion. In this case, PapC gathers the "parts" that make up the adhesive and then guides the assembled adhesive out of the cell.
Li and his colleagues found that PapC consists of two main structural elements, with each part containing one opening, or pore. Each pore is approximately two nanometers (billionths of a meter) in diameter, and the entire structure is 11 nanometers in length and seven nanometers wide.
While this structure might suggest that PapC uses both pores simultaneously, the researchers think that only one of the two pores may be in use at once.
Contact: Laura Mgrdichian
DOE/Brookhaven National Laboratory