Amorphous calcium carbonate (ACC) is an important precursor phase for the formation of aragonite crystals in the shells of Pinctada fucata. To identify the ACC-binding protein in the inner aragonite layer of the shell, extracts from the shell were used in the ACC-binding experiments. Semiquantitative analyses using liquid chromatography–mass spectrometry revealed that paramyosin was strongly associated with ACC in the shell. We discovered that paramyosin, a major component of the adductor muscle, was included in the myostracum, which is the microstructure of the shell attached to the adductor muscle. Purified paramyosin accumulates calcium carbonate and induces the prism structure of aragonite crystals, which is related to the morphology of prism aragonite crystals in the myostracum. Nuclear magnetic resonance measurements revealed that the Glu-rich region was bound to ACC. Activity of the Glu-rich region was stronger than that of the Asp-rich region. These results suggest that paramyosin in the adductor muscle is involved in the formation of aragonite prisms in the myostracum.

中文翻译：

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珠母贝壳中无定形碳酸钙结合蛋白副肌球蛋白的结构和功能分析

无定形碳酸钙（ACC）是珠母贝贝壳中文石晶体形成的重要前体相。为了鉴定壳内文石层中的 ACC 结合蛋白，将壳提取物用于 ACC 结合实验。使用液相色谱-质谱法的半定量分析表明，副肌球蛋白与壳中的 ACC 密切相关。我们发现，内收肌的主要成分副肌球蛋白包含在肌层中，肌层是附着在内收肌上的外壳的微观结构。纯化的副肌球蛋白积累碳酸钙并诱发文石晶体的棱柱结构，这与肌层中棱柱文石晶体的形态有关。核磁共振测量表明富含 Glu 的区域与 ACC 结合。富含Glu的区域的活性强于富含Asp的区域的活性。这些结果表明内收肌中的副肌球蛋白参与肌层文石棱柱的形成。