An acidic matrix protein, Pif, is a key macromolecule for nacre formation.

Suzuki, Michio; Saruwatari, Kazuko; Kogure, Toshihiro; Yamamoto, Yuya; Nishimura, Tatsuya; Kato, Takashi; Nagasawa, Hiromichi · Science · 2009

basic_science · Level V

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Abstract

The mollusk shell is a hard tissue consisting of calcium carbonate crystals and an organic matrix. The nacre of the shell is characterized by a stacked compartment structure with a uniformly oriented c axis of aragonite crystals in each compartment. Using a calcium carbonate-binding assay, we identified an acidic matrix protein, Pif, in the pearl oyster Pinctada fucata that specifically binds to aragonite crystals. The Pif complementary DNA (cDNA) encoded a precursor protein, which was posttranslationally cleaved to produce Pif 97 and Pif 80. The results from immunolocalization, a knockdown experiment that used RNA interference, and in vitro calcium carbonate crystallization studies strongly indicate that Pif regulates nacre formation.

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