Max-Planck-Institut für Biochemie, Abteilung Proteomics und Signaltransduktion, D-82152 Martinsried, Am Klopferspitz 18, Germany.
Proteome Sci. 2010 Jun 17;8:33. doi: 10.1186/1477-5956-8-33.
The sea urchin embryo has been an important model organism in developmental biology for more than a century. This is due to its relatively simple construction, translucent appearance, and the possibility to follow the fate of individual cells as development to the pluteus larva proceeds. Because the larvae contain tiny calcitic skeletal elements, the spicules, they are also important model organisms for biomineralization research. Similar to other biominerals the spicule contains an organic matrix, which is thought to play an important role in its formation. However, only few spicule matrix proteins were identified previously.
Using mass spectrometry-based methods we have identified 231 proteins in the matrix of the S. purpuratus spicule matrix. Approximately two thirds of the identified proteins are either known or predicted to be extracellular proteins or transmembrane proteins with large ectodomains. The ectodomains may have been solubilized by partial proteolysis and subsequently integrated into the growing spicule. The most abundant protein of the spicule matrix is SM50. SM50-related proteins, SM30-related proteins, MSP130 and related proteins, matrix metalloproteases and carbonic anhydrase are among the most abundant components.
The spicule matrix is a relatively complex mixture of proteins not only containing matrix-specific proteins with a function in matrix assembly or mineralization, but also: 1) proteins possibly important for the formation of the continuous membrane delineating the mineralization space; 2) proteins for secretory processes delivering proteinaceous or non-proteinaceous precursors; 3) or proteins reflecting signaling events at the cell/matrix interface. Comparison of the proteomes of different skeletal matrices allows prediction of proteins of general importance for mineralization in sea urchins, such as SM50, SM30-E, SM29 or MSP130. The comparisons also help point out putative tissue-specific proteins, such as tooth phosphodontin or specific spicule matrix metalloproteases of the MMP18/19 group. Furthermore, the direct sequence analysis of peptides by MS/MS validates many predicted genes and confirms the existence of the corresponding proteins.
海洋海胆胚胎在发育生物学中已经成为一个重要的模式生物超过一个世纪。这是由于其相对简单的结构，半透明的外观，以及随着幼虫发育为幼形幼虫，有可能跟踪单个细胞的命运。由于幼虫含有微小的碳酸钙骨骼元素，即骨针，因此它们也是生物矿化研究的重要模式生物。与其他生物矿化物质相似，骨针含有有机基质，据认为该有机基质在其形成中起着重要作用。然而，之前只鉴定了少数骨针基质蛋白。
使用基于质谱的方法，我们已经在 S. purpuratus 骨针基质的基质中鉴定出 231 种蛋白质。鉴定出的蛋白质约有三分之二是已知的或预测为细胞外蛋白或具有大胞外域的跨膜蛋白。胞外域可能通过部分蛋白水解而溶解，并随后整合到正在生长的骨针中。骨针基质中最丰富的蛋白是 SM50。SM50 相关蛋白、SM30 相关蛋白、MSP130 和相关蛋白、基质金属蛋白酶和碳酸酐酶是最丰富的成分之一。
骨针基质是一种相对复杂的蛋白质混合物，不仅包含在基质组装或矿化中具有功能的基质特异性蛋白，还包含：1）可能对形成连续膜以划定矿化空间很重要的蛋白；2）用于分泌过程以输送蛋白或非蛋白前体的蛋白；3）或反映细胞/基质界面信号事件的蛋白。不同骨骼基质的蛋白质组比较可以预测对海胆矿化具有普遍重要性的蛋白质，如 SM50、SM30-E、SM29 或 MSP130。比较还可以帮助指出可能的组织特异性蛋白，如牙齿磷蛋白或特定的 MMP18/19 组骨针基质金属蛋白酶。此外，通过 MS/MS 对肽的直接序列分析验证了许多预测基因的存在，并证实了相应蛋白质的存在。
