A Comparative Study of the Shell Matrix Protein Aspein in Pterioid Bivalves
A Comparative Study of the Shell Matrix Protein Aspein in Pterioid Bivalves
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DOI：
10.1007/s00239-012-9514-3
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发表时间：
2012-08-01
影响因子：
3.9
通讯作者：
Endo, Kazuyoshi
中科院分区：
文献类型：
--
作者：
Isowa, Yukinobu;Sarashina, Isao;Endo, Kazuyoshi
Aspein是最初从合浦珠母贝中鉴定出的一种异常酸性的壳基质蛋白。Aspein被认为在壳的形成中起重要作用，特别是在棱柱层中的方解石沉淀中。在这项研究中，我们确定了Aspein同源物从三个密切相关的pterioid物种：大珠母贝，Isognomon佩尔纳，和Pteria企鹅。我们的免疫分析表明，它们存在于方解石棱柱层，但不是在文石nacritic层的壳。序列比较表明Ser-Glu-Pro和Asp-Ala重复基序在Aspein同源物中是保守的，表明它们在功能上是重要的。所有Aspein同系物检查共享Asp-rich D-域，这表明该域可能在碳酸钙形成中具有非常重要的功能。然而，序列分析显示，即使在非常密切相关的物种中，D-结构域中的天冬氨酸的排列也存在显着的高水平变异。这一观察结果表明，D-结构域的功能并不需要Asp的特定排列。
Aspein is one of the unusually acidic shell matrix proteins originally identified from the pearl oyster Pinctada fucata. Aspein is thought to play important roles in the shell formation, especially in calcite precipitation in the prismatic layer. In this study, we identified Aspein homologs from three closely related pterioid species: Pinctada maxima, Isognomon perna, and Pteria penguin. Our immunoassays showed that they are present in the calcitic prismatic layer but not in the aragonitic nacreous layer of the shells. Sequence comparison showed that the Ser-Glu-Pro and the Asp-Ala repeat motifs are conserved among these Aspein homologs, indicating that they are functionally important. All Aspein homologs examined share the Asp-rich D-domain, suggesting that this domain might have a very important function in calcium carbonate formation. However, sequence analyses showed a significantly high level of variation in the arrangement of Asp in the D-domain even among very closely related species. This observation suggests that specific arrangements of Asp are not required for the functions of the D-domain.