UMR CNRS 6282 Biogeosciences, University of Burgundy - Franche-Comté, 6 Boulevard Gabriel, 21000 DIJON, France.
Schulich Faculty of Chemistry and Russell Berrie Nanotechnology Institute Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel.
J Struct Biol. 2020 Jul 1;211(1):107507. doi: 10.1016/j.jsb.2020.107507. Epub 2020 Apr 15.
Molluscs are one of the most diversified phyla among metazoans. Most of them produce an external calcified shell, resulting from the secretory activity of a specialized epithelium of the calcifying mantle. This biomineralization process is controlled by a set of extracellular macromolecules, the organic matrix. In spite of several studies, these components are mainly known for bivalves and gastropods. In the present study, we investigated the physical and biochemical properties of the internal planispiral shell of the Ram's Horn squid Spirula spirula. Scanning Electron Microscope investigations of the shell reveal a complex microstructural organization. The saccharides constitute a quantitatively important moiety of the matrix, as shown by Fourier-transform infrared and solid-state nuclear magnetic resonance spectroscopies. NMR identified β-chitin and additional polysaccharides for a total amount of 80% of the insoluble fraction. Proteomics was applied to both soluble and insoluble matrices and in silico searches were performed, first on heterologous metazoans models, and secondly on an unpublished transcriptome of Spirula spirula. In the first case, several peptides were identified, some of them matching with tyrosinase, chitinase 2, protease inhibitor, or immunoglobulin. In the second case, 39 hits were obtained, including transferrin, a serine protease inhibitor, matrilin, or different histones. The very few similarities with known molluscan shell matrix proteins suggest that Spirula spirula uses a unique set of shell matrix proteins for constructing its internal shell. The absence of similarity with closely related cephalopods demonstrates that there is no obvious phylogenetic signal in the cephalopod skeletal matrix.
软体动物是后生动物中最多样化的一门。它们大多数都有一个外部的钙化壳，这是由有分泌功能的专门的钙化套膜上皮细胞产生的。这个生物矿化过程是由一组细胞外的大分子，即有机基质来控制的。尽管有几项研究，但这些成分主要是在双壳类和腹足类中被了解。在本研究中，我们研究了拉姆氏角石蛸（ Spirula spirula ）内部平面螺旋形贝壳的物理和生化特性。对贝壳的扫描电子显微镜研究揭示了其复杂的微观组织结构。傅立叶变换红外光谱和固态核磁共振波谱表明，糖构成了基质的一个重要的定量部分。NMR 鉴定了β-几丁质和其他多糖，其总量占不溶性部分的 80%。蛋白质组学被应用于可溶性和不溶性基质，并且首先在异源后生动物模型上，其次在 Spirula spirula 的未发表的转录组上进行了计算机搜索。在第一种情况下，鉴定出了几种肽，其中一些与酪氨酸酶、壳质酶 2、蛋白酶抑制剂或免疫球蛋白匹配。在第二种情况下，获得了 39 个命中，包括转铁蛋白、丝氨酸蛋白酶抑制剂、基质金属蛋白酶抑制剂或不同的组蛋白。与已知的软体动物贝壳基质蛋白的极少数相似性表明，拉姆氏角石蛸使用一组独特的贝壳基质蛋白来构建其内部贝壳。与亲缘关系密切的头足类动物缺乏相似性表明，头足类动物的骨骼基质中没有明显的系统发育信号。
