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Response of E. coli to m-Tyrosine

ABSTRACT: To ensure faithful translation of the genetic code, some aminoacyl-tRNA synthetases have a quality control (QC) mechanism that allows them to remove similarly shaped, non-protein amino acids (NPAs) from a mischarged tRNA. In E. coli, the QC function of phenyalanyl-tRNA synthetase (PheRS) is required for resistantce to the toxic NPA, meta-Tyrosine (m-Tyr). Here, we sought to understand the mechanism of m-Tyr toxicity. Using RNA-seq, we observed >500 genes were differential expressed after the addition of m-Tyr. The most strongly up-regulated genes are involved in unfolded-protein stress response, and cells exposed to m-Tyr contained large, electron-dense protein aggregates, indicating that m-Tyr destabilized a large fraction of the proteome. Additionally, we observed that amino acid biosynthesis and transport regulons, controlled by ArgR, TrpR, and TyrR, and the stringent-response regulon, controlled by DksA/ppGpp, were differentially expressed. m-Tyr resistant mutants were isolated and found to have altered a promoter to increase expression of the enzymes for Phe production or to have altered transporters, which likely result in less uptake or increased efflux of m-Tyr. These findings indicate that QC by PheRS is the critical point for resisting the toxic effects of m-Tyr, when m-Tyr has passed the QC checkpoint and enters the proteome, it is sequestered in protein aggregates that are eventually lost through cell division.

ORGANISM(S): Escherichia coli

PROVIDER: GSE140211 | GEO | 2020/11/30

REPOSITORIES: GEO

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