Control of electrostatic interactions between F-actin and genetically modified lysozyme in aqueous media
Control of electrostatic interactions between F-actin and genetically modified lysozyme in aqueous media
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DOI：
10.1073/pnas.0705898104
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发表时间：
2007-10-09
影响因子：
11.1
通讯作者：
Wong, Gerard C. L.
中科院分区：
文献类型：
--
作者：
Sanders, Lori K.;Xian, Wujing;Wong, Gerard C. L.
确定控制水介质中宏离子之间相互作用的目的激发了广泛的实验和理论工作。虽然已经确定，在带相反电荷的凝聚剂的影响下，带相同电荷的大分子可以聚集，但这种聚集稳定性的具体条件只能通过经验来确定。我们通过使用一个由f -肌动蛋白（一种阴离子棒状聚电解质）和溶菌酶（一种带电荷的阳离子球状蛋白，可以进行基因修饰）组成的定义良好的模型系统来研究这些涉及静电和渗透效应相互作用的条件。利用同步x射线散射和分子动力学模拟研究了不同溶菌酶电荷突变体和盐浓度下肌动蛋白-溶菌酶复合物的结构和稳定性。我们提供的证据支持f -肌动蛋白的结构转变，从在肌动蛋白亚晶格的三层间隙位置由溶菌酶阵列结合在一起的柱状排列到溶菌酶位于肌动蛋白之间的两层桥接位置的边缘稳定的复合物。稳定性的降低是由于盐在络合物和周围溶液之间的分配大大减少。肌动蛋白-溶菌酶复合物稳定性的变化具有生物医学意义，因为据报道，它们的形成通过隔离溶菌酶等抗菌素导致囊性纤维化患者气道感染的持续存在。我们提出了x射线显微镜结果，证明囊性纤维化痰中存在肌动蛋白-溶菌酶复合物，并证明，在广泛的盐条件下，电荷还原溶菌酶在保持其杀死细菌活性的同时，不会被隔离在有序的复合物中。
The aim for deterministic control of the interactions between macroions in aqueous media has motivated widespread experimental and theoretical work. Although it has been well established that like-charged macromolecules can aggregate under the influence of oppositely charged condensing agents, the specific conditions for the stability of such aggregates can only be determined empirically. We examine these conditions, which involve an interplay of electrostatic and osmotic effects, by using a well defined model system composed of F-actin, an anionic rod-like polyelectrolyte, and lysozyme, a cationic globular protein with a charge that can be genetically modified. The structure and stability of actin-lysozyme complexes for different lysozyme charge mutants and salt concentrations are examined by using synchrotron x-ray scattering and molecular dynamics simulations. We provide evidence that supports a structural transition from columnar arrangements of F-actin held together by arrays of lysozyme at the threefold interstitial sites of the actin sublattice to marginally stable complexes in which lysozyme resides at twofold bridging sites between actin. The reduced stability arises from strongly reduced partitioning of salt between the complex and the surrounding solution. Changes in the stability of actin-lysozyme complexes are of biomedical interest because their formation has been reported to contribute to the persistence of airway infections in cystic fibrosis by sequestering antimicrobials such as lysozyme. We present x-ray microscopy results that argue for the existence of actin-lysozyme complexes in cystic fibrosis sputum and demonstrate that, for a wide range of salt conditions, charge-reduced lysozyme is not sequestered in ordered complexes while retaining its bacterial killing activity.