Component of the outer cell wall layer. Required for stability of the cell wall and for optimal growth. Required for resistance against several antifungal and cell wall-perturbing agents and for tolerance to heat shock. Covalently attached to the cell wall. Positively regulated by signaling through MPK1 in response to cell wall perturbation. Induced by heat shock and nitrogen starvation. Expression is also regulated by the ACE2 and SWI5 transcription factors. The PIR1/2/3 repeats are required for the covalent linkage to the cell wall (By similarity). Their number varies among different strains of S.cerevisiae. Covalently linked to beta-1,3-glucan of the inner cell wall layer via an alkali-sensitive ester linkage between the gamma-carboxyl group of glutamic acids, arising from specific glutamines within the PIR1/2/3 repeats, and hydroxyl groups of glucoses of beta-1,3-glucan chains. The propeptide is cleaved off in the late Golgi. While both peptides are secreted, only a fraction of the mature glycoprotein is incorporated into the cell wall. O-glycosylated. Extensively O-mannosylated. Present with 14600 molecules/cell in log phase SD medium. Belongs to the PIR protein family.