Structures of mollusc shell framework proteins

Mollusc shells consist of the nacreous mother-of-pearl layer and the prismatic layer. Both layers are microlaminate composites of CaCO3 crystals (aragonite in the nacre and calcite in the prismatic layer) and biopolymers. The main biopolymers are structural proteins, insoluble in water and methanoic acid, which determine the framework of each shell layer and bind soluble polyanionic proteins which determine the type of CaCO3 crystal that grows. Here we report the sequences and structures of the framework proteins for the nacreous and prismatic layers of the pearl oyster, Pinctada fucata.