Structural basis of calcification inhibition by α2-HS glycoprotein/fetuin-A -: Formation of colloidal calciprotein particles
Structural basis of calcification inhibition by α2-HS glycoprotein/fetuin-A -: Formation of colloidal calciprotein particles
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DOI：
10.1074/jbc.m210868200
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发表时间：
2003-04-11
影响因子：
4.8
通讯作者：
Jahnen-Dechent, W
中科院分区：
文献类型：
--
作者：
Heiss, A;DuChesne, A;Jahnen-Dechent, W
来自突变小鼠的遗传证据表明，α(2)-HS糖蛋白/胎球蛋白-A(Ahsg)是一种系统性的碱性磷酸钙沉淀抑制物，可防止不必要的钙化。利用电子显微镜和动态光散射，我们证明了AHsG对沉淀的抑制是由于含有AHsG、钙和磷酸盐的可溶性胶体球体的瞬时形成所致。这些直径为30-150 nm的“钙蛋白颗粒”最初是无定形的和可溶的，但随着时间和温度的变化，逐渐变得更结晶化和不可溶。含AHsG的钙蛋白颗粒的增溶作用为解释不溶性钙沉淀物如何在哺乳动物体内运输和清除提供了一个新的概念框架。突变分析表明，碱性磷酸钙沉淀抑制活性位于Ahsg的氨基末端类cystatin结构域。对Ahsg、全长胎球蛋白B、富含组氨酸的糖蛋白和激肽原的野生型和突变型半胱氨酸类结构域的结构-功能分析表明，Ahsg结构域D1在抑制碱性磷酸钙沉淀方面最有效。计算机模拟的结构域结构表明，胱抑素样结构域Ahsg-D1的扩展β-折叠上致密的酸性残基阵列介导了有效的抑制。
Genetic evidence from mutant mice suggests that alpha(2)-HS glycoprotein/fetuin-A (Ahsg) is a systemic inhibitor of precipitation of basic calcium phosphate preventing unwanted calcification. Using electron microscopy and dynamic light scattering, we demonstrate that precipitation inhibition by Ahsg is caused by the transient formation of soluble, colloidal spheres, containing Ahsg, calcium, and phosphate. These "calciprotein particles" of 30-150 nm in diameter are initially amorphous and soluble but turn progressively more crystalline and insoluble in a time- and temperature-dependent fashion. Solubilization in Ahsg-containing calciprotein particles provides a novel conceptual framework to explain how insoluble calcium precipitates may be transported and removed in the bodies of mammals. Mutational analysis showed that the basic calcium phosphate precipitation inhibition activity resides in the amino-terminal cystatin-like domain D1 of Ahsg. A structure-function analysis of wild type and mutant forms of cystatin-like domains from Ahsg, full-length fetuin-B, histidine-rich glycoprotein, and kininogen demonstrated that Ahsg domain D1 is most efficient in inhibiting basic calcium phosphate precipitation. The computer-modeled domain structures suggest that a dense array of acidic residues on an extended beta-sheet of the cystatin-like domain Ahsg-D1 mediates efficient inhibition.