珍珠质水溶性基质蛋白的分离纯化及其对碳酸钙结晶的影响

Extraction and purification of water soluble matrix protein from nacre and its effect on CaCO_3 crystallization

珍珠质是由大于95 %的碳酸钙晶体与少量有机大分子组成的生物矿化产物 ,其中含量小于5%的基质蛋白 (matrixprotein)对碳酸钙晶体的形成进行严格控制。为深入研究珍珠质基质蛋白对碳酸钙结晶的调控作用 ,本研究利用水提法从合浦珠母贝 (Pinctadafucata)珍珠质中提取出水溶性基质 (WaterSolubleMatrix,WSM) ,并利用反相HPLC分离得到3个主要蛋白组分(FI-III)。氨基酸组成分析表明 ,WSM及其3种组分富含甘氨酸、天冬氨酸、丙氨酸与亮氨酸。体外饱和碳酸钙溶液结晶实验表明 ,WSM能显著影响体外碳酸钙晶体的形成 ;其3种组分对碳酸钙晶体形成的作用并不相同 :组分FI和组分FII加速晶体的形成 ,而组分III则抑制晶体的形成。本研究首次发现在珍珠质中同时存在抑制和促进晶体形成的两种蛋白质因子 ,推测珍珠质致密有序结构的形成是正。

Nacre, the internal lustrous “mother of pearl” layer of many common shells, is a biomineral product of mainly CaCO3 crystals and a matrix of biological macromolecules. Depite constituting less than 5% of total nacre weight, matrix proteins control the crystallization of CaCO3. To further investigate the regulatory function of Water Soluble Matrix (WSM) in nacre biomineralization, aqueous extraction was used to extract WSM from the Pinctada fucata nacre. Three protein fractions (FI～III) have been separated and collected from the WSM by reversed phase HPLC. According to the results of amino acid composition analysis, WSM and the three fractions are rich in glycine, alanine, aspartate, and leucine. Crystallization experiment in vitro showed that WSM and the three fractions markedly affected CaCO3 crystal formation. The three fractions however,have different effects on the CaCO3 crystallization. FI and FII stimulate CaCO3 formation, while FIII has suppressive effect on CaCO3 formation. This is the first identification of two proteins factors in WSM which stimulate and suppress CaCO3 crystallization separately indicating nacre formation is under both positive and negative regulations.