Every summer, warm waters bathe the west coast of the United States, Canada, and other parts of the world in toxic algae. Particularly frightening are dinoflagellates in the genus Gonyaulax, Alexandrium, Gymnodinium, and Pyrodinium, which secrete saxitoxin, one of the world’s most lethal neurotoxins. Shellfish swallow saxitoxin and concentrate it in their bodies so readily that eating just one saxitoxin-laden mussel can cause paralysis and even death. Despite government warnings, people are poisoned every year by mussels they’ve gathered and eaten—as are birds, whales, and seals. But algae eaters—including shellfish, pufferfish, and freshwater frogs—remain blissfully unaffected.
Since the 1990s, scientists have known that these animals are naturally resistant to saxitoxin: they make proteins that sequester saxitoxin so it can’t affect their nervous systems. Recently, a team led by Daniel Minor, a biophysicist at the University of California, San Francisco, has taken on a molecular investigationof the novel phenomenon.
Minor and his colleagues used X-ray crystallography—the same technique used to first identify the structure of DNA—to create an atomic-resolution picture of saxiphilin, an antitoxin protein collected from American bullfrogs. They could see, in intricate detail, how saxiphilin binds with saxitoxin to render it harmless. This sophisticated image could bring researchers one step closer to detecting saxitoxin and dozens of other similar marine toxins, and even developing an antitoxin.
Detection may prove ever more essential in coming years. As climate change begets rising ocean temperatures and the deoxygenation of coastal waters, algal blooms worldwide are becoming bigger and lasting longer. More algal blooms mean more toxin-laden seafood and more sick humans, birds, and seals. If the trend continues, a better toxin detector will be a vital part of public health efforts. (...)
To protect the public, the department routinely tests for saxitoxin and other marine toxins at hundreds of spots along the coast every week. But the saxitoxin test used at the time—and still in use today—was developed in the 1930s and involves dosing mice with toxic seawater and seeing how long it takes them to die. Some people think the test is inhumane, considering how many mice must die to confirm the quality of the water. But the test remains the quickest and cheapest approach available. (...)
In his new study, Minor focused on identifying the physical structure of saxiphilin and found that it is shaped somewhat like a butterfly. Saxitoxin binds at an indented spot on one of the wings. The pocket fits saxitoxin snugly and is negatively charged, attracting the toxin electrostatically. To Minor’s surprise, the binding site looks almost exactly the same as when saxitoxin binds to sodium channels in human nerve cells, which means that saxiphilin might work to mitigate the effects of saxitoxin in people, too.
Since the 1990s, scientists have known that these animals are naturally resistant to saxitoxin: they make proteins that sequester saxitoxin so it can’t affect their nervous systems. Recently, a team led by Daniel Minor, a biophysicist at the University of California, San Francisco, has taken on a molecular investigationof the novel phenomenon.Minor and his colleagues used X-ray crystallography—the same technique used to first identify the structure of DNA—to create an atomic-resolution picture of saxiphilin, an antitoxin protein collected from American bullfrogs. They could see, in intricate detail, how saxiphilin binds with saxitoxin to render it harmless. This sophisticated image could bring researchers one step closer to detecting saxitoxin and dozens of other similar marine toxins, and even developing an antitoxin.
Detection may prove ever more essential in coming years. As climate change begets rising ocean temperatures and the deoxygenation of coastal waters, algal blooms worldwide are becoming bigger and lasting longer. More algal blooms mean more toxin-laden seafood and more sick humans, birds, and seals. If the trend continues, a better toxin detector will be a vital part of public health efforts. (...)
To protect the public, the department routinely tests for saxitoxin and other marine toxins at hundreds of spots along the coast every week. But the saxitoxin test used at the time—and still in use today—was developed in the 1930s and involves dosing mice with toxic seawater and seeing how long it takes them to die. Some people think the test is inhumane, considering how many mice must die to confirm the quality of the water. But the test remains the quickest and cheapest approach available. (...)
In his new study, Minor focused on identifying the physical structure of saxiphilin and found that it is shaped somewhat like a butterfly. Saxitoxin binds at an indented spot on one of the wings. The pocket fits saxitoxin snugly and is negatively charged, attracting the toxin electrostatically. To Minor’s surprise, the binding site looks almost exactly the same as when saxitoxin binds to sodium channels in human nerve cells, which means that saxiphilin might work to mitigate the effects of saxitoxin in people, too.
by Casey Rentz, Hakai Magazine | Read more:
Image: Rolf Nussbaumer/NPL/Minden Pictures
