FIG 1.

Scheme for autoregulation of Pdc1 synthesis. (A) In S. cerevisiae, a hypothetical protein, Era, together with an activating protein A (Pdc2?), activates the transcription of PDC1. The Pdc1 protein in the cytosol would sequester the activating protein and decrease PDC1 transcription (50). (B) In K. lactis, transcription of KlPDC1 is activated by the regulatory protein Rag3, an ortholog of Pdc2. When the concentration of Pdc1 is high, most of the Rag3 protein is bound to it and trapped in the cytosol; consequently, the rate of KlPDC1 transcription is low. When Pdc1 levels decrease, Rag3 is liberated and can enter the nucleus, activating KlPDC1 transcription (52).