With EXP1, the specific cargo receptor protein for the plasma membrane ATPase PMA1, is involved in the transport and/or maturation of PMA1 (PubMed:28727280). EXP1 and PSG1 probably act sequentially to promote PMA1 sorting between the ER and the Golgi, with EXP1 promoting PMA1 export from the ER to the Golgi while PSG1 has a role in PMA1 maturation or quality control in the Golgi (PubMed:28727280). PSG1 might also couple PMA1 sorting and maturation in the early secretory pathway with the glycosylation machinery (Probable). PSG1 is cleaved by KEX2 in two stable peptides, PSG1-N' and PSG1-C', the former supporting a role in maturation quality control, the latter having a role in modulating vesicular trafficking. Interacts with EXP1 (PubMed:28727280). PSG1-N' interacts with ERAD-related proteins involved in PMA1 quality control including EPS1, CDC48, UBX2 and SSM4 (PubMed:28727280). PSG1-C' interacts with the TLG1/2 SNARE complex proteins TLG1, TLG2 and VTI1 (PubMed:28727280). The precursor protein is cleaved into two polypeptide chains, PSG1-N' and PSG1-C'. The cleavage is performed in the Golgi apparatus by Ca(+)-dependent serine protease KEX2 between Arg-229 and Asp-230. PSG1-N' is highly O-mannosylated. Leads to enhanced degradation of PMA1 in the vacuole. Present with 606 molecules/cell in log phase SD medium.