Scientists capture recluse spider toxin killing cells
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- Researchers led by former student Alexandra Sundman crystallized and X-rayed a toxin from the Chilean six-eyed sand spider (a relative of the brown recluse) bound to cell-membrane target molecules, producing the first clear view of the enzyme's active site with substrates in its 'mouth.'
- The recluse toxin is an enzyme that scoots along cell surfaces like a lawn mower, clipping molecular heads off and rearranging them into ring structures, a mechanism first discovered by former lab member Dan Lajoie and now visualized in 3D.
- Structural comparison of the toxin before and after binding showed it changes shape upon attaching to a cell surface, suggesting the enzyme is activated only once it docks with its target — a finding that points to two new intervention points (blocking binding or blocking the chemical cut).
- In the United States, the brown recluse (necrotic toxin causing tissue destruction) and the black widow (nerve-cell neurotoxin) are the two spiders of major medical concern, but no approved treatments exist domestically for recluse bites; antivenoms are available only in South America.
- Recluse bites can cause serious skin lesions sometimes requiring grafts, may damage red blood cells, and can lead to life-threatening kidney failure, and the lesions are frequently misdiagnosed as methicillin-resistant Staphylococcus infections.
- The team, working across the author's lab and collaborator Greta Binford's group, hopes the new structure will let scientists design drugs that either stop the toxin from binding to cells or prevent it from chemically remodeling their surfaces.
Why it matters: With no approved US treatment for recluse bites and lesions routinely misdiagnosed as drug-resistant staph infections, a precise atomic map of the toxin gives drug developers a concrete target for the first time — potentially enabling a therapeutic that could prevent the skin grafts, red-blood-cell damage, and kidney failure that make severe bites life-threatening.
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