ATP与Fe4S4*络合的31P-NMR研究

MgATP结合在铁蛋白的什么部位?众说纷芸,尚无定论。大多数研究者认为,MgATP不是与铁蛋白的活性中心Fe_4S_4原子簇络合,而是与它的非铁部位例如巯基或者外围组织络合。在上述作用模式中,ATP与铁蛋白键合的性质是不确定的。曾主张MgATP与铁蛋白的非铁部位结合的Mortenson等后来用~(31)P-NMR观察到,MgATP与还原态铁蛋白的结合,引起ATP的α-、β-和γ-~(31)P谱峰分别往低磁场漂移8.7、9和7.7ppm,这时他开始认为,这种变化可能是由于ATP与铁蛋白的某部位或者是与其活性中心Fe_4S_4原子簇的络合引起的。铁蛋白的活性中心与其模型化合物在化学性质上是基本相似的。通过化学模拟体系的~(31)P-NMR研究,有助于确定铁蛋白与MgATP的络合方式。

~(31)P NMR STUDIES ON COMPLEXATION OF Fe_4S_4~* WITH ATP

Chemical modeling studies of ATP driven electron-transfer in Nitrogenase reaction show that adenylate compounds can complex with Fe_4S_4(SPh)_4]~(2-) cluster, resulting in down field shifting of the ~(31)P NMR peaks of α-、β- and γ-PO_4 about 13.2ppm. 8.3ppm and 28.3ppm, respectively (in its DMF-D_2O(3:2v/v) solution). in down-field shifting of the ~(31)p NMR peaks of a-and β-PO_4 of ADP by about 15.77ppm and 2.71ppm respectively. (in DMF-D_2O (3:2v/v) solution). The above experimental results is quite similar to the observations of Mortenson et al in Fe-protein system. This may be taken as the strong evidence for supporting the view that all of the MgATP and the MgADP can coordinate to the Fe_4S_4~* center of the Fe-protein through the PO_4 groups, rather than other parts of theprotein.