Robach J S, Stock S R, Veis A
Department of Cell and Molecular Biology, Northwestern University, Chicago, IL 60611-3008, USA.
J Struct Biol. 2006 Jul;155(1):87-95. doi: 10.1016/j.jsb.2006.03.002. Epub 2006 Mar 29.
Mature portions of sea urchin are comprised of a complex array of reinforcing elements yet are single crystals of high and very high Mg calcite. How a relatively poor structural material (calcite) can produce mechanically competent structures is of great interest. In teeth of the sea urchin Lytechinus variegatus, we recorded high-resolution secondary ion mass spectrometry (SIMS) maps of Mg, Ca ,and specific amino acid fragments of mineral-related proteins including aspartic acid (Asp). SIMS revealed strong colocalization of Asp residues with very high Mg. Demineralized specimens showed serine localization on membranes between crystal elements and reduced Mg and aspartic acid signals, further emphasizing colocalization of very high Mg with ready soluble Asp-rich protein(s). The association of Asp with nonequilibrium, very high magnesium calcite provides insight to the makeup of the macromolecules involved in the growth of two different composition calcites and the fundamental process of biomineralization.
海胆的成熟部分由一系列复杂的增强元素组成，但却是高镁方解石和非常高镁方解石的单晶。一种相对较差的结构材料（方解石）如何能产生机械性能良好的结构，这一点非常令人感兴趣。在多棘刺海胆的牙齿中，我们记录了镁、钙以及与矿物质相关蛋白质的特定氨基酸片段（包括天冬氨酸）的高分辨率二次离子质谱（SIMS）图谱。SIMS显示天冬氨酸残基与非常高的镁有很强的共定位。脱矿质标本显示丝氨酸定位于晶体元素之间的膜上，同时镁和天冬氨酸信号减弱，这进一步强调了非常高的镁与易溶性富含天冬氨酸的蛋白质的共定位。天冬氨酸与非平衡态、非常高镁方解石的关联，为参与两种不同成分方解石生长的大分子组成以及生物矿化的基本过程提供了见解。
