The Mechanism of β-N-methylamino-l-alanine Inhibition of tRNA Aminoacylation and Its Impact on Misincorporation

Authors

Nien-Ching Han, The Ohio State University
Tammy J. Bullwinkle, The Ohio State University
Kaeli F. Loeb, The Ohio State University
Kym F. Faull, University of California, Los Angeles
Kyle Mohler, Yale University
Jesse Rinehart, Yale University
Michael Ibba, Chapman UniversityFollow

Document Type

Article

Publication Date

1-31-2021

Abstract

β-N-methylamino-l-alanine (BMAA) is a nonproteinogenic amino acid that has been associated with neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD). BMAA has been found in human protein extracts; however, the mechanism by which it enters the proteome is still unclear. It has been suggested that BMAA is misincorporated at serine codons during protein synthesis, but direct evidence of its cotranslational incorporation is currently lacking. Here, using LC-MS–purified BMAA and several biochemical assays, we sought to determine whether any aminoacyl-tRNA synthetase (aaRS) utilizes BMAA as a substrate for aminoacylation. Despite BMAA's previously predicted misincorporation at serine codons, following a screen for amino acid activation in ATP/PP_i exchange assays, we observed that BMAA is not a substrate for human seryl-tRNA synthetase (SerRS). Instead, we observed that BMAA is a substrate for human alanyl-tRNA synthetase (AlaRS) and can form BMAA-tRNA^Ala by escaping from the intrinsic AlaRS proofreading activity. Furthermore, we found that BMAA inhibits both the cognate amino acid activation and the editing functions of AlaRS. Our results reveal that, in addition to being misincorporated during translation, BMAA may be able to disrupt the integrity of protein synthesis through multiple different mechanisms.

Comments

This article was originally published in Journal of Biological Chemistry, volume 295, issue 5, in 2021. https://doi.org/10.1016/S0021-9258(17)49898-X

Recommended Citation

Han, N-C., Bullwinkle, T.J., Loeb, K.F., Faull, K.F., Mohler, K., Rinehart, J., Ibba, M. The mechanism of β-N-methylamino-L-alanine inhibition of tRNA aminoacylation and its impact on misincorporation. J. Biol. Chem. 2020; 295(5): 1402-1410. https://doi.org/10.1016/S0021-9258(17)49898-X

Copyright

The authors

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.