To find out, Culotta's lab joined forces with Mak Saito, a marine chemist at WHOI, who had developed techniques to explore how marine life uses metals. Saito was particularly intrigued because of the high incidence of Lyme Disease on Cape Cod, where WHOI is located, and because he specializes in metalloproteins, which contain iron, zinc, cobalt, and other elements often seen in vitamin supplements. The metals serve as linchpins, binding to enzymes. They help determine the enzymes' distinctive three-dimensional shapes and the specific chemical reactions they catalyze.
It's difficult to identify what metals are within proteins because typical analyses break apart proteins, often separating metal from protein. Saito used a liquid chromatography mass spectrometer to distinguish and measure separate individual Borrelia proteins according to their chemical properties and infinitesimal differences in their masses. Then he used an inductively coupled plasma mass spectrometer to detect and measure metals down to parts per trillion. Together, the combined analyses not only measured the amounts of metals and proteins, they showed that the metals are components of the proteins.
"The tools he has are fantastic," Culotta said. "Not too many people have this set of tools to detect metalloproteins."
The experiments revealed that instead of iron, Borrelia uses that element's next-door neighbor on the periodic chart, manganese, in certain Borrelia enzymes. These include an amino peptidase and an important antioxidant enzyme called superoxide dismutase.
Superoxide dismutase protects the pathogens against a second defense mechanism that the body throws against them. The body bombards pathogens with superoxide radicals, highly reactive molecules that cause damage within the pathogens. Superoxide dismutase is like an antioxidant that neutralizes the s
|Contact: Media Relations Office|
Woods Hole Oceanographic Institution