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submitted on 23.09.2020 and posted on 24.09.2020by Katie Mae Wilson, Aurora Burkus-Matesevac, Samuel Maddox, Christopher Chouinard
β-methylamino-L-alanine (BMAA) has been linked to the development of
neurodegenerative (ND) symptoms following chronic environmental exposure through water and
dietary sources. The brains of those affected by this condition, often referred to as amyotrophic
lateral sclerosis-parkinsonism-dementia complex (ALS-PDC), have exhibited the presence of
plaques and neurofibrillary tangles (NFTs) from protein aggregation. Although numerous studies
have sought to better understand the correlation between BMAA exposure and onset of ND
symptoms, no definitive link has been identified. One prevailing hypothesis is that BMAA acts a
small molecule ligand, complexing with critical proteins in the brain and reducing their function.
The objective of this research was to investigate the effects of BMAA exposure on the native
structure of ubiquitin. We hypothesized that formation of a Ubiquitin+BMAA noncovalent
complex would alter the protein’s structure and folding and ultimately affect the ubiquitinproteasome system (UPS) and the unfolded protein response (UPR). Ion mobility-mass
spectrometry revealed that at sufficiently high concentrations BMAA did in fact form a
noncovalent complex with ubiquitin, however similar complexes were identified for a range of
additional amino acids. Collision induced unfolding (CIU) was used to interrogate the unfolding
dynamics of native ubiquitin and these Ubq-amino acid complexes and it was determined that
complexation with BMAA led to a significant alteration in native protein size and conformation,
and this complex required considerably more energy to unfold. This indicates that the complex
remains more stable under native conditions and this may indicate that BMAA has attached to a
critical binding location.