Download MendeleyNon-specific activities of the major herbicide-resistance gene BAR.
Christ, B., Hochstrasser, R., Guyer, L., Francisco, R., Aubry, S., Hortensteiner, S., Weng, J.K.(2017) Nat Plants 3: 937-945
- PubMed: 29180815
- DOI: https://doi.org/10.1038/s41477-017-0061-1
- Primary Citation of Related Structures:
5T7D, 5T7E - PubMed Abstract:
Bialaphos resistance (BAR) and phosphinothricin acetyltransferase (PAT) genes, which convey resistance to the broad-spectrum herbicide phosphinothricin (also known as glufosinate) via N-acetylation, have been globally used in basic plant research and genetically engineered crops 1-4 . Although early in vitro enzyme assays showed that recombinant BAR and PAT exhibit substrate preference toward phosphinothricin over the 20 proteinogenic amino acids 1 , indirect effects of BAR-containing transgenes in planta, including modified amino acid levels, have been seen but without the identification of their direct causes 5,6 . Combining metabolomics, plant genetics and biochemical approaches, we show that transgenic BAR indeed converts two plant endogenous amino acids, aminoadipate and tryptophan, to their respective N-acetylated products in several plant species. We report the crystal structures of BAR, and further delineate structural basis for its substrate selectivity and catalytic mechanism. Through structure-guided protein engineering, we generated several BAR variants that display significantly reduced non-specific activities compared with its wild-type counterpart in vivo. The transgenic expression of enzymes can result in unintended off-target metabolism arising from enzyme promiscuity. Understanding such phenomena at the mechanistic level can facilitate the design of maximally insulated systems featuring heterologously expressed enzymes.
Organizational Affiliation:
Whitehead Institute for Biomedical Research, Cambridge, MA, 02142, USA.
