Chemists from UCLA and the University of Florence in Italy report that they have found evidence that suggests that in ALS patients, copper-zinc superoxide dismutase, which is associated with the disease, may not contain copper and zinc at all.
“If we keep the metals entirely out of the protein, we can explain the toxicity, since even the normal protein forms aggregate at physiological conditions when the metals are gone,” explains Joan Selverstone Valentine, UCLA professor of chemistry and biochemistry.
“We studied what happens to the protein if you have the metals, if you have no metals, and if you have part of the metals,” Valentine says. The research indicates that it is the metal-free protein that is likely to be toxic. The protein misfolds when the copper and zinc are not present but folds properly when they are there. “Before copper and zinc are inserted, the protein can misfold under physiological conditions,” Valentine explains.
There is evidence that ALS is associated with this misfolding of the protein, which becomes toxic in some way that is not known and has properties similar to misfolded proteins associated with other neurodegenerative disorders like Alzheimer’s and Parkinson’s disease, according to Valentine.
The team presented evidence for this hypothesis in Proceedings of the National Academy of Sciences, currently online and available in the journal’s July 3 print edition.