Figure 7. Model for Rgg2/3-SHP2/3 regulation.

The pro-SHP peptide is subject to processing by Eep and is secreted by an unknown transporter. Once exported, a secondary processing step may produce active SHP (and, as seen in Figure 5D, process sSHP3). The oligopeptide permease (Opp) imports SHP to the cytoplasm where the pheromone directly engages Rgg proteins. In the absence of SHP, Rgg3 represses transcription of shp promoters. De-repression occurs upon Rgg3 binding of either peptide, whereas Rgg2-SHP interactions facilitate transcription activation.