Comparative evaluation of retrograde regulatory proteins (Rtg1p, Rtg2p, and Rtg3p) of Saccharomyces cerevisiae and Pichia pastoris and identification of P. pastoris RtgXp as a novel regulator of multiple metabolic pathways

Abstract

Our work demonstrates for the first time that PpRtgXp, a basic, helix-loop-helix (bHLH) protein, is a global regulator of carbon metabolism. PpRtgXp constitutively localizes inside the nucleus. Despite lacking the C-terminal leucine zipper heterodimerization domain, this bHLH protein evolved into a unique regulator of multiple metabolic pathways of P. pastoris. This is the first report on a bHLH protein functioning as a global transcriptional regulator in P. pastoris as previous studies have focussed primarily on zinc finger transcription factors such as Mxr1p, Trm1p, and Rop1p