Liu Honglin, Yin Peidong, He Shengnan, Sun Zhihu, Tao Ye, Huang Yan, Zhuang Hao, Zhang Guobin, Wei Shiqiang
National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, People's Republic of China.
Biochem Biophys Res Commun. 2010 Jul 2;397(3):598-602. doi: 10.1016/j.bbrc.2010.06.005. Epub 2010 Jun 4.
To understand the role of ATP underlying the enhanced amyloidosis of hen egg white lysozyme (HEWL), the synchrotron radiation circular dichroism, combined with tryptophan fluorescence, dynamic light-scattering, and differential scanning calorimetry, is used to examine the alterations of the conformation and thermal unfolding pathway of the HEWL in the presence of ATP, Mg(2+)-ATP, ADP, AMP, etc. It is revealed that the binding of ATP to HEWL through strong electrostatic interaction changes the secondary structures of HEWL and makes the exposed residue W62 move into hydrophobic environments. This alteration of W62 decreases the beta-domain stability of HEWL, induces a noncooperative unfolding of the secondary structures, and produces a partially unfolded intermediate. This intermediate containing relatively rich alpha-helix and less beta-sheet structures has a great tendency to aggregate. The results imply that the ease of aggregating of HEWL is related to the extent of denaturation of the amyloidogenic region, rather than the electrostatic neutralizing effect or monomeric beta-sheet enriched intermediate.
为了解三磷酸腺苷（ATP）在鸡蛋清溶菌酶（HEWL）淀粉样变性增强过程中的作用，利用同步辐射圆二色光谱结合色氨酸荧光、动态光散射和差示扫描量热法，研究了在ATP、Mg(2+)-ATP、二磷酸腺苷（ADP）、一磷酸腺苷（AMP）等存在下HEWL的构象变化和热解折叠途径。结果表明，ATP通过强静电相互作用与HEWL结合，改变了HEWL的二级结构，使暴露在外的残基W62进入疏水环境。W62的这种变化降低了HEWL的β结构域稳定性，诱导二级结构的非协同解折叠，并产生部分解折叠中间体。这种含有相对丰富α螺旋和较少β折叠结构的中间体具有很强的聚集倾向。结果表明，HEWL的聚集倾向与淀粉样生成区域的变性程度有关，而不是与静电中和作用或富含单体β折叠的中间体有关。
