Cell surface protein required for proper cell wall integrity and for the correct assembly of the mannoprotein outer layer of the cell wall. Mostly targeted to the plasma membrane. Expression is induced by growth in hypoxic conditions and by caspofungin and ketoconazole. Expression is negatively regulated by BCR1, HOG1, PLC1, RIM101, SSN6, and SUR7. Belongs to the SPS2 family.