Structural and functional analysis and its application of the yeast novel N-asetylransferase that detoxifies a proline analogue

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The MPR1 gene (sigma 1278b gene for proline-analogue resistance) of the budding yeast Saccharomyces cerevisiae, which is found in the Σ1278b strain, encodes a novel N-acetyltransferase (Mpr1) that detoxifies the proline analogue azetidine-2-carboxylate (AZC). In this study, we analyzed the structure and function of Mpr1 as follows.1)We found that mpr1-disrupted cells were hypersensitive to oxidative stresses such as H_2O_2 and heat shock and contained increased levels of reactive oxygen species (ROS). In contrast, expression of MPR1 leads to a decrease in ROS level and an increase in cell viability after oxidative treatments. These results indicate that Mpr1 can reduce intracellular ROS levels. It was also found that put2-disrupted yeast cells lacking Δ^1-pyrroline-5-carboxylate (P5C) dehydrogenease increased ROS levels and put2-disrupted cells that expressed MPR1 had considerably lower ROS levels. Mpr1 acetylates P5C or its equilibrium compound glutamtate-γ-semialdehyde. These results … More suggest that P5C is toxic to yeast cells due to the formation of ROS and that Mpr1 regulates the ROS level under P5C-induced oxidative stress.2) We found that yeast cells exhibited increased levels of ROS during freezing and thawing. Gene disruption and expression experiments indicated that Mpr1 protects yeast cells from freezing stress by reducing the intracellular levels of ROS. Similar results were obtained from ethanol stress. Similar results were obtained from ethanol stress. Gene disruption and expression experiments indicated that Mpr1 protect yeast cells from ethanol stress by reducing the intracellular ROS.3) We investigated whether MPR1 would function similarly in bacterial and plant cells and if its expression could confer resistance to AZC. Our studies confirm that MPR1 can function in a similar fashion in Escherichia coli and tobacco as in yeast to detoxify the toxic AZC so could potentially be used as a new selectable marker for E.coli and plant transformation.In summary, as a novel antioxidant mechanism, Mpr1 is supposed to reduce the intracellular oxidation level by acetylating the toxic metabolite(s) involved in ROS production, such as P5C/GSA. The proposed role of Mpr1 against oxidative stress could be promising for breeding novel stress-resistant yeast strains. Less