Zhang Yong, Xie Liping, Meng Qingxiong, Jiang Tiemin, Pu Ruolei, Chen Lei, Zhang Rongqing
Department of Biological Sciences and Biotechnology, Tsinghua University, HaiDian, 100084, Beijing, PR China.
Comp Biochem Physiol B Biochem Mol Biol. 2003 Jul;135(3):565-73. doi: 10.1016/s1096-4959(03)00138-6.
Understanding the molecular composition is of great interest for both nacre formation mechanism and biomineralization in mollusk shell. A cDNA clone encoding an MSI31 relative, termed MSI7 because of its estimated molecular mass of 7.3 kDa, was isolated from the pearl oyster, Pinctada fucata. This novel protein shares similarity with MSI31, a prismatic framework protein of P. fucata. It is peculiar that MSI7 is much shorter in size, harboring only the Gly-rich sequence that has been proposed to be critical for Ca(2+) binding. In situ hybridization result showed that MSI7 mRNA was expressed specifically at the folds and outer epithelia of the mantle, indicating that MSI7 participates in the framework formation of both the nacreous layer and prismatic layer. In vitro experiment on the function of MSI7 suggested that it accelerates the nucleation and precipitation of CaCO(3). Taken together, we have identified a novel matrix protein of the pearl oyster, which may play an important role in determining the texture of nacre.
了解分子组成对于珍珠母形成机制和软体动物贝壳中的生物矿化都具有重要意义。从合浦珠母贝中分离出一个编码MSI31相关蛋白的cDNA克隆，因其估计分子量为7.3 kDa而被命名为MSI7。这种新蛋白与MSI31相似，MSI31是合浦珠母贝的一种棱柱层框架蛋白。特别的是，MSI7的大小要短得多，仅含有被认为对Ca(2+)结合至关重要的富含甘氨酸的序列。原位杂交结果表明，MSI7 mRNA在套膜的褶皱和外层上皮细胞中特异性表达，这表明MSI7参与了珍珠层和棱柱层的框架形成。关于MSI7功能的体外实验表明，它能加速CaCO(3)的成核和沉淀。综上所述，我们鉴定出了一种合浦珠母贝的新型基质蛋白，它可能在决定珍珠层质地方面发挥重要作用。
