Max-Planck-Institut für Biochemie, Abteilung Proteomics und Signaltransduktion, D-82152 Martinsried, Am Klopferspitz 18, Germany.
Proteome Sci. 2010 Feb 8;8(1):6. doi: 10.1186/1477-5956-8-6.
Sea urchin is a major model organism for developmental biology and biomineralization research. However, identification of proteins involved in larval skeleton formation and mineralization processes in the embryo and adult, and the molecular characterization of such proteins, has just gained momentum with the sequencing of the Strongylocentrotus purpuratus genome and the introduction of high-throughput proteomics into the field.
The present report contains the determination of test (shell) and tooth organic matrix phosphoproteomes. Altogether 34 phosphoproteins were identified in the biomineral organic matrices. Most phosphoproteins were specific for one compartment, only two were identified in both matrices. The sea urchin phosphoproteomes contained several obvious orthologs of mammalian proteins, such as a Src family tyrosine kinase, protein kinase C-delta 1, Dickkopf-1 and other signal transduction components, or nucleobindin. In most cases phosphorylation sites were conserved between sea urchin and mammalian proteins. However, the majority of phosphoproteins had no mammalian counterpart. The most interesting of the sea urchin-specific phosphoproteins, from the perspective of biomineralization research, was an abundant highly phosphorylated and very acidic tooth matrix protein composed of 35 very similar short sequence repeats, a predicted N-terminal secretion signal sequence, and an Asp-rich C-terminal motif, contained in [Glean3:18919].
The 64 phosphorylation sites determined represent the most comprehensive list of experimentally identified sea urchin protein phosphorylation sites at present and are an important addition to the recently analyzed Strongylocentrotus purpuratus shell and tooth proteomes. The identified phosphoproteins included a major, highly phosphorylated protein, [Glean3:18919], for which we suggest the name phosphodontin. Although not sequence-related to such highly phosphorylated acidic mammalian dental phosphoproteins as phosphoryn or dentin matrix protein-1, phosphodontin may perform similar functions in the sea urchin tooth. More than half of the detected proteins were not previously identified at the protein level, thus confirming the existence of proteins only known as genomic sequences previously.
海胆是发育生物学和生物矿化研究的主要模式生物。然而，在胚胎和成体中参与幼虫骨骼形成和矿化过程的蛋白质的鉴定以及这些蛋白质的分子特征，随着 Strongylocentrotus purpuratus 基因组的测序和高通量蛋白质组学在该领域的引入，才刚刚起步。
本报告包含测试（壳）和牙齿有机基质磷酸蛋白组的测定。在生物矿化有机基质中总共鉴定出 34 种磷酸蛋白。大多数磷酸蛋白特异性存在于一个隔室中，只有两种被鉴定为存在于两种基质中。海胆磷酸蛋白组包含几种哺乳动物蛋白质的明显同源物，如Src 家族酪氨酸激酶、蛋白激酶 C-delta 1、Dickkopf-1 和其他信号转导成分，或核结合蛋白。在大多数情况下，磷酸化位点在海胆和哺乳动物蛋白质之间是保守的。然而，大多数磷酸蛋白没有哺乳动物对应物。从生物矿化研究的角度来看，海胆特有的磷酸蛋白中最有趣的是一种丰富的高度磷酸化且非常酸性的牙齿基质蛋白，由 35 个非常相似的短序列重复组成，预测有一个 N 端分泌信号序列和一个富含 Asp 的 C 端基序，包含在 [Glean3:18919] 中。
目前确定的 64 个磷酸化位点代表了目前实验鉴定的海胆蛋白质磷酸化位点的最全面列表，是最近分析的 Strongylocentrotus purpuratus 壳和牙齿蛋白质组的重要补充。鉴定出的磷酸蛋白包括一种主要的、高度磷酸化的蛋白质 [Glean3:18919]，我们建议将其命名为磷酸牙蛋白。虽然与高度磷酸化的酸性哺乳动物牙蛋白如磷酸蛋白或牙本质基质蛋白 1 没有序列关系，但磷酸牙蛋白可能在海胆牙齿中发挥类似的功能。检测到的蛋白质中超过一半以前没有在蛋白质水平上被鉴定，因此证实了以前仅作为基因组序列已知的蛋白质的存在。
