Effect of zinc, copper, and calcium on the structure and stability of serum amyloid A.
Effect of zinc, copper, and calcium on the structure and stability of serum amyloid A.
复制标题
锌、铜和钙对血清淀粉样蛋白 A 结构和稳定性的影响。
DOI：
10.1021/bi602629y
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发表时间：
2007
期刊：
影响因子：
2.9
通讯作者：
Colon,Wilfredo
中科院分区：
文献类型：
--
作者：
Wang,Limin;Colon,Wilfredo
血清淀粉样蛋白A(SAA)是一种高度保守的急性时相反应蛋白，在炎性刺激后，其血清浓度可增加到∼的1000倍。SAA主要与血清中的高密度脂蛋白有关，其主要功能可能涉及胆固醇转运和脂代谢。然而，SAA也与许多其他功能和一些疾病有关，尽管这些潜在的联系仍然知之甚少。SAA的三维结构尚不清楚，但我们已经证明，小鼠SAA2.2可以作为边缘稳定的六角体存在于溶液中，它在37℃时解离为一种单体物种，该单体物种不可逆转地错误折叠并自组装成淀粉样纤维。因此，当SAA与其他蛋白质或小配体结合时，它在体内的结构和功能似乎受到了调节。本文用四级结构、三级结构和二级结构的各种探针研究了水溶液中铜(Cu2+)、锌(Zn2+)和钙(Ca2+)对SAA2.2结构和稳定性的影响。在不同的金属浓度下，包括在血清中发现的那些，结果表明，不同的金属类型和浓度对SAA2.2的结构和稳定性有不同的影响。发现铜(10−100μM)使六聚体的平衡向单体方向移动，而对三级结构和二级结构的稳定性没有显著影响。相反，锌(1−10μM)与SAA2.2结合并稳定其四级、三级和二级结构。钙(1−，10 mM)破坏了SAA2.2结构的所有元件的稳定性，并在10 mM处诱导其聚集。当SAA2.2与1 mM的Cu2+或Zn2+孵育时，也观察到SAA2.2的完全聚集，进一步证明了SAA2.2的细小结构和稳定性。因此，这些结果表明，SAA的许多功能和病理作用可能依赖于其不稳定的结构，在动态平衡条件下和在急性时相反应中，SAA与配体的相互作用调节了SAA的结构。
Serum amyloid A (SAA) is a highly conserved acute phase reactant protein, and its concentration in serum can increase up to ∼1000 times after an inflammatory stimuli. SAA is mainly associated with high-density lipoproteins in serum, and its main function appears to involve cholesterol transport and lipid metabolism. However, SAA has also been associated with many other functions and a number of diseases, although these potential links remain poorly understood. The three-dimensional structure of SAA is not known, but we have shown that murine SAA2.2 can exist in solution as a marginally stable hexamer, which at 37 °C dissociates to a monomeric species that misfolds irreversibly and self-assembles into amyloid fibrils. Thus, the structure and function of SAA in vivo appear to be modulated when it binds to other proteins or small ligands. Herein, the effect of copper (Cu2+), zinc (Zn2+), and calcium (Ca2+) on the structure and stability of SAA2.2 in aqueous solution was examined using various probes of quaternary, tertiary, and secondary structure. At different concentrations of metals, including those found in the serum, the results show that the structure and stability of SAA2.2 are differently affected depending on the metal type and concentration. Copper (10−100 μM) was found to shift the equilibrium from hexamer to monomer without affecting significantly the stability of the tertiary and secondary structure of SAA2.2. In contrast, zinc (1−10 μM) bound to SAA2.2 and stabilized its quaternary, tertiary, and secondary structure. Calcium (1−10 mM) destabilized all elements of SAA2.2 structure and induced its aggregation at 10 mM. Complete aggregation of SAA2.2 was also observed when it was incubated with 1 mM Cu2+or Zn2+, further demonstrating the tenuous structure and stability of SAA2.2. Thus, these results suggest that the many functional and pathological roles attributed to SAA may rely on its precarious structure, modulated by its interaction with ligands under homeostasis conditions and during the acute phase response.