Expressed in mantle distal zone, mantle margin and grafted pearl pockets. Not expressed in adductor muscle, gills, hemocytes or ungrafted pearl pockets. Within the mantle, specifically expressed in mineralizing outer epithelium cells (at protein level). After secretion incorporated into acid-insoluble nacre matrix of shell and pearl (at protein level). Not found in acid-insoluble matrix of shell prisms (at protein level).