Zhao Guang-Hua, Yu Ping, Hu Xiao-Song, Zhao Lei
College of Food Science & Nutritional Engineering, China Agricultural University, Beijing 100083, China.
Acta Biochim Biophys Sin (Shanghai). 2004 Feb;36(2):99-104. doi: 10.1093/abbs/36.2.99.
Only beta-NGF, the subunit of the 7S NGF complex, exhibits NGF activity, but the function of the zinc ion in native beta-NGF has received little attention. Flameless atomic absorption spectroscopy (FAAS) measurements reveal that native beta-NGF contains Zn(II) with a Zn(II)/beta-NGF stoichiometry of 1:14.6. The presence of Zn(II) in the native molecule results in significant changes of the secondary structure and local tertiary structure around Trp(s) with respect to those of apo beta-NGF, as suggested by spectra of fluorescence and circular dichrosim. Stopped-flow studies show that there are at least two steps during the interaction of Zn(II) with the apo form. In comparison with its apo form, the native beta-NGF shows a higher ability to trigger the proliferation of TF1 cells and mediate the survival of PC12. Thus it is most likely that the structural changes caused by the presence of Zn(II) directly lead to the increase in the biological activity of beta-NGF. All results indicate that Zn(II) in native beta-NGF plays an important role in the structure and the biological activity of the protein.
只有β-NGF（7S NGF复合物的亚基）具有NGF活性，但天然β-NGF中锌离子的功能却很少受到关注。无焰原子吸收光谱法（FAAS）测量显示，天然β-NGF含有Zn（II），其Zn（II）/β-NGF化学计量比为1:14.6。如荧光光谱和圆二色光谱所示，天然分子中Zn（II）的存在导致色氨酸周围的二级结构和局部三级结构相对于脱辅基β-NGF发生显著变化。停流研究表明，Zn（II）与脱辅基形式相互作用过程中至少有两个步骤。与脱辅基形式相比，天然β-NGF显示出更高的触发TF1细胞增殖和介导PC12细胞存活的能力。因此，很可能是Zn（II）的存在引起的结构变化直接导致了β-NGF生物活性的增加。所有结果表明，天然β-NGF中的Zn（II）在该蛋白质的结构和生物活性中起重要作用。
