Ykl077w/Psg1 (Pma1 Stabilization in the Golgi) physically interacts with Exp1 (for ER eXport of Pma1). Psg1 can be found in the Golgi and coat protein I (COPI) vesicles but does not directly bind Pma1. Loss of Psg1 causes enhanced degradation of Pma1 in the vacuole. Psg1 is 392aa protein with a predicted signal sequence at its N-terminus and a single TMD near the C-terminus. The short cytosolic region bears 2 putative retrieval motifs KRR and KKxxKxx. It was previously shown to be cleaved by the Ca+ dependent serine protease, Kex2 [1].

1: Two novel effectors of trafficking and maturation of the yeast plasma membrane H(+) -ATPase. Geva Y, Crissman J, Arakel EC, Gomez-Navarro N, Chuartzman SG, Stahmer KR, Schwappach B, Miller EA, Schuldiner M; Traffic. 2017;18:672-682. PMID:28727280