Mann Karlheinz, Poustka Albert J, Mann Matthias
Max-Planck-Institut für Biochemie, Martinsried, Am Klopferspitz, Germany.
Proteome Sci. 2008 Aug 11;6:22. doi: 10.1186/1477-5956-6-22.
The organic matrix of biominerals plays an important role in biomineral formation and in determining biomineral properties. However, most components of biomineral matrices remain unknown at present. In sea urchin, which is an important model organism for developmental biology and biomineralization, only few matrix components have been identified and characterized at the protein level. The recent publication of the Strongylocentrotus purpuratus genome sequence rendered possible not only the identification of possible matrix proteins at the gene level, but also the direct identification of proteins contained in matrices of skeletal elements by in-depth, high-accuracy, proteomic analysis.
We identified 110 proteins as components of sea urchin test and spine organic matrix. Fourty of these proteins occurred in both compartments while others were unique to their respective compartment. More than 95% of the proteins were detected in sea urchin skeletal matrices for the first time. The most abundant protein in both matrices was the previously characterized spicule matrix protein SM50, but at least eight other members of this group, many of them only known as conceptual translation products previously, were identified by mass spectrometric sequence analysis of peptides derived from in vitro matrix degradation. The matrices also contained proteins implicated in biomineralization processes previously by inhibition studies using antibodies or specific enzyme inhibitors, such as matrix metalloproteases and members of the mesenchyme-specific MSP130 family. Other components were carbonic anhydrase, collagens, echinonectin, a alpha2-macroglobulin-like protein and several proteins containing scavenger receptor cysteine-rich domains. A few possible signal transduction pathway components, such as GTP-binding proteins, a semaphorin and a possible tyrosine kinase were also identified.
This report presents the most comprehensive list of sea urchin skeletal matrix proteins available at present. The complex mixture of proteins identified in matrices of the sea urchin skeleton may reflect many different aspects of the mineralization process. Because LC-MS/MS-based methods directly measures peptides our results validate many predicted genes and confirm the existence of the corresponding proteins. Considering the many newly identified matrix proteins, this proteomic study may serve as a road map for the further exploration of biomineralization processes in an important model organism.
生物矿物的有机基质在生物矿化形成及决定生物矿物特性方面发挥着重要作用。然而，目前生物矿物基质的大多数成分仍不为人知。海胆是发育生物学和生物矿化研究的重要模式生物，在蛋白质水平上仅鉴定和表征了少数基质成分。紫海胆基因组序列的近期公布，不仅使得在基因水平上鉴定可能的基质蛋白成为可能，还能通过深入、高精度的蛋白质组学分析直接鉴定骨骼元素基质中所含的蛋白质。
我们鉴定出110种蛋白质作为海胆壳和棘有机基质的成分。其中40种蛋白质在两个部位均有出现，而其他蛋白质则各自在其特定部位存在。超过95%的蛋白质是首次在海胆骨骼基质中被检测到。两种基质中最丰富的蛋白质是先前已表征的骨针基质蛋白SM50，但通过对体外基质降解产生的肽段进行质谱序列分析，还鉴定出了该蛋白家族的至少其他八个成员，其中许多成员此前仅作为概念性翻译产物为人所知。这些基质还包含先前通过使用抗体或特定酶抑制剂进行抑制研究而涉及生物矿化过程的蛋白质，如基质金属蛋白酶和间充质特异性MSP130家族的成员。其他成分包括碳酸酐酶、胶原蛋白、海胆粘连蛋白、一种α2-巨球蛋白样蛋白以及几种含有富含半胱氨酸清道夫受体结构域的蛋白质。还鉴定出了一些可能的信号转导途径成分，如GTP结合蛋白、一种信号素和一种可能的酪氨酸激酶。
本报告列出了目前可用的最全面的海胆骨骼基质蛋白清单。在海胆骨骼基质中鉴定出的复杂蛋白质混合物可能反映了矿化过程的许多不同方面。由于基于液相色谱-串联质谱的方法直接测量肽段，我们的结果验证了许多预测基因并证实了相应蛋白质的存在。考虑到许多新鉴定出的基质蛋白，这项蛋白质组学研究可为进一步探索这一重要模式生物中的生物矿化过程提供路线图。
