The interactome of the Bakers' yeast peroxiredoxin Tsa1 implicates it in redox regulation of intermediary metabolism, glycolysis, and zinc homeostasis

Abstract

Zinc (Zn) is an essential nutrient supporting a range of critical processes. In the yeast Saccharomyces cerevisiae, Zn deficiency induces a transcriptional response mediated by the Zap1 activator, which controls a regulon of ∼80 genes. A subset support Zn homeostasis by promoting Zn uptake and its distribution between compartments, while the remainder mediate an 'adaptive response' to enhance fitness of Zn-deficient (ZnD) cells. The peroxiredoxin Tsa1 is a Zap1-regulated adaptive factor essential for the growth of ZnD yeast. Tsa1 can function as an antioxidant peroxidase, protein chaperone, or redox sensor: The latter activity oxidizes associated proteins via a redox relay mechanism. We previously reported that in ZnD cells, Tsa1 inhibits pyruvate kinase (Pyk1) to conserve phosphoenolpyruvate for aromatic amino acid synthesis. However, this regulation makes a relatively minor contribution to fitness in low Zn, suggesting that Tsa1 targets other pathways important to adaptation. Consistent with this model, the redox sensor function of Tsa1 was essential for growth of ZnD cells. Using a maltose binding protein-tagged version of Tsa1, we identified a redox-sensitive non-covalent interaction with Pyk1, and applied this system to identify multiple novel interacting partners. This interactome implicates Tsa1 in the regulation of critical processes including many Zn-dependent metabolic pathways. Interestingly, Zap1 is a Tsa1 target, as Tsa1 strongly promoted the oxidation of Zap1 activation domain 2 and was required for full Zap1 activity. Our findings reveal a novel posttranslational response to Zn deficiency, overlain on and interconnected with the Zap1-mediated transcriptional response.