Activation of the oxidative stress regulator PpYap1 through conserved cysteine residues during methanol metabolism in the yeast Pichia pastoris

Abstract

The methylotrophic yeast Pichia pastoris can grow on methanol as sole source of carbon and energy. The first reaction in yeast methanol metabolism, catalyzed by an abundant peroxisomal enzyme, alcohol oxidase, generates high levels of H2O2, but the oxidative stress response during methanol metabolism has not been elucidated. In this study, we isolated the Yapl homolog of P. pastoris (PpYapl) and analyzed the properties of a PpYAPl-disruption strain. The PpYapl transcription factor is activated after exposure to various reactive agents, and therefore functions as a regulator of the redox system in P. pastoris. We have also identified PpGPXl, the unique glutathione peroxidase-encoding gene in P. pastoris whose expression is induced by PpYapl. PpGpxl, but not the ScTsal or SpTpxl homolog PpTsal, functions as a H2O2 sensor and activates PpYapl. This study is the first demonstration of a yeast Yapl family protein activated during conventional metabolism.