The family of nerve-damaging toxins produced by Clostridium botulinum is so deadly it is classified as one of the most dangerous potential bioterrorism agents. Although botulism, the illness the toxins cause, is rare, it can paralyze and kill.
There are seven known types of botulinum toxin produced by various C. botulinum strains, designated by the letters A through G. Toxins A and B, identified in 1919, are used therapeutically to control muscle spasms, chronic pain, and overactive bladder, and cosmetically to smooth wrinkles. In 1969, toxin G was discovered, and, in 2013, there was a brief flurry of interest over what seemed to be the discovery of type H. Gene sequencing, however, showed it to be a combination of a subtype of toxin F and a piece of toxin A.
There is now, however, new cause for interest. Min Dong, an HMS assistant professor of surgery at Boston Children’s Hospital, and colleagues have reported a new botulinum toxin. Provisionally called toxin X, it has properties that set it apart from its cousins. The study appeared August 3 in Nature Communications.
“Sequence-wise, it doesn’t look like any other toxin,” says Dong, “and it cannot be recognized by antibodies to any other known botulinum toxin.”
Dong’s team showed that botulinum toxin X cleaves the same set of nerve proteins targeted by other botulinum toxins but that it also cleaves a group of proteins that none of the other toxins touch. These proteins are poorly characterized, so toxin X may be a tool that researchers can use to better define the proteins’ functions. These additional protein targets might endow toxin X with new, medically relevant properties.
Since each toxin requires a separate antibody to neutralize it, learning of this new botulinum toxin may allow doctors and researchers to better defend against botulism.
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