Golgi-to-late endosome trafficking of the yeast pheromone processing enzyme Ste13p is regulated by a phosphorylation site in its cytosolic domain.

This study addressed whether phosphorylation regulates trafficking of yeast membrane proteins that cycle between the trans-Golgi network (TGN) and endosomal system. The TGN membrane proteins A-ALP, a model protein containing the Ste13p cytosolic domain fused to alkaline phosphatase (ALP), and Kex2p were found to be phosphorylated in vivo. Mutation of the S13 residue on the cytosolic domain of A-ALP to Ala was found to block trafficking to the prevacuolar compartment (PVC), whereas a S13D mutation generated to mimic phosphorylation accelerated trafficking into the PVC.