β- N-Methylamino-l-alanine (BMAA) Not Involved in Alzheimer's Disease.

β- N-Methylamino-l-alanine (BMAA) is a neurotoxic agent implicated in ALS as well as Parkinson's and Alzheimer's diseases. It is produced by blue-green algae and could find its way via fish and seafood into the human food supply. Isolation from biological samples yields the compound in monomeric and protein-bound form. It has been suggested that the protein-bound fraction may result from genetic misincorporation into proteins in place of serine. Concomitant misfolding of the mutated proteins may be responsible for the neurological diseases. Recent reports that contradict the misincorporation theory leave unresolved the nature of the protein-bound form of BMAA. We have found from quantum mechanical calculations on model systems that it is possible to bind BMAA with high affinity in a noncovalent fashion to proteins. Because of our interest in Alzheimer's disease, molecular dynamics simulations were applied to search for such binding between BMAA and the β-amyloid peptide and to discover whether replacement of either of its two serine residues could affect its aggregation into neurotoxic oligomers. No stable noncovalently bound complex was found, and it was concluded that incorporation of BMAA in place of serine would not alter the conformational dynamics of the β-amyloid peptide.