Marin Frédéric, Narayanappa Prabakaran, Motreuil Sébastien
UMR CNRS 5561 "Biogéosciences", Université de Bourgogne, Dijon, France,
Prog Mol Subcell Biol. 2011;52:353-95. doi: 10.1007/978-3-642-21230-7_13.
In molluscs, the shell secretion process is controlled by a set of extracellular macromolecules collectively called the shell matrix. The shell matrix, which is produced by the mantle epithelial cells during mineralization, is predominantly composed of proteins, glycoproteins, acidic polysaccharides, and chitin that precisely regulate the deposition of calcium carbonate outside the mantle cells. In the present paper, we focus on the shell of Pinna nobilis, the giant Mediterranean fan mussel, usually considered as a model for studying molluscan biomineralization processes. P. nobilis exhibits indeed a nacro-prismatic shell, the outer layer of which is constituted of the so-called "regular simple calcitic prisms," according to Carter and Clark (1985). We review here the microstructural characteristics of the prisms and nacre and the biochemical properties of their associated matrices. In particular, the calcitic prisms of P. nobilis are characterized by a cortege of unusually acidic intraprismatic proteins, while the ones of the nacreous layer seem less acidic. A brief description of the molecular characterization of three acidic proteins, caspartin, calprismin and mucoperlin, is given. In particular, we show that extremely acidic intracrystalline proteins such as caspartin interact with calcium carbonate at different scales, from micrometric to crystal lattice levels.
在软体动物中，贝壳分泌过程由一组统称为贝壳基质的细胞外大分子控制。贝壳基质由外套膜上皮细胞在矿化过程中产生，主要由蛋白质、糖蛋白、酸性多糖和几丁质组成，它们精确调节碳酸钙在外套膜细胞外的沉积。在本文中，我们关注的是大砗磲（Pinna nobilis）的贝壳，这种巨大的地中海扇贝通常被视为研究软体动物生物矿化过程的模型。根据卡特和克拉克（1985年）的研究，大砗磲确实具有珍珠棱柱层贝壳，其外层由所谓的“规则简单方解石棱柱”组成。我们在此回顾棱柱和珍珠层的微观结构特征及其相关基质的生化特性。特别是，大砗磲的方解石棱柱的特征是含有一系列异常酸性的棱柱内蛋白质，而珍珠层的蛋白质酸性似乎较低。本文简要描述了三种酸性蛋白，即天冬氨酸壳蛋白、钙棱柱蛋白和黏液珍珠蛋白的分子特征。特别是，我们表明，像天冬氨酸壳蛋白这样的极端酸性晶内蛋白在从微米级到晶格级的不同尺度上与碳酸钙相互作用。
