INTERACTION OF ADENOSINE 5'-TRIPHOSPHATE WITH MG-2+ - VIBRATIONAL STUDY OF COORDINATION SITES BY USE OF O-18-LABELED TRIPHOSPHATES
INTERACTION OF ADENOSINE 5'-TRIPHOSPHATE WITH MG-2+ - VIBRATIONAL STUDY OF COORDINATION SITES BY USE OF O-18-LABELED TRIPHOSPHATES
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DOI：
10.1021/ja00210a013
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发表时间：
1988-01-20
影响因子：
15
通讯作者：
HARADA, I
中科院分区：
文献类型：
--
作者：
TAKEUCHI, H;MURATA, H;HARADA, I
对三磷酸腺苷（ATP）及其三种同位素异构体（其三磷酸氧原子被选择性地用\(^{18}O\)取代）进行了红外光谱和拉曼光谱测量。观察到的\(^{18}O\)取代引起的频率位移使得确定每个磷酸基团（\(\alpha\)、\(\beta\)或\(\gamma\)）对红外和拉曼谱带的贡献成为可能。发现ATP或\(^{18}O\)标记的ATP的几个红外谱带可归因于主要涉及三个磷酸基团之一的振动。这种局域振动在复合物形成时的频率位移对于研究\(Mg^{2+}\)与ATP的配位位点是有用的。在pH 3.0时，观察到位于单个\(PO_2^{-}\)基团的振动有相当的频率位移，同时一些ATP分子中由于构象异构化导致主链振动强度发生变化。这些红外数据可解释为是由于\(\alpha,\beta - \)、\(\beta,\gamma - \)和\(\alpha,\gamma - \)双齿配位体共存。在pH 7.5时，\(\alpha - PO_2^{-}\)振动的频率位移与pH 3.0时相同，而\(\beta - PO_2^{-}\)振动的频率位移是pH 3.0时的两倍。频率位移数据也表明\(Mg^{2+}\)与\(\gamma - PO_3^{2 - }\)有类似的强相互作用。因此，在pH 7.5时的\(MgATP\)被认为是\(\beta,\gamma - \)双齿和\(\alpha,\beta,\gamma - \)三齿复合物的混合物。讨论了本研究结果对涉及\(MgATP\)的酶促反应的影响。
Infrared and Raman spectra were measured of ATP and its three isotopomers whose triphosphate oxygen atoms were selectively substituted by 18O. The observed frequency shifts on 18O-substitution made it possible to determine the contributions of each phosphate group (.alpha., .beta., or .gamma.) to the infrared and Raman bands. Several infrared bands of ATP or 18O-labeled ATP were found to be assignable to vibrations predominantly involving one of the three phosphate groups. Frequency shifts of such localized vibrations on complex formation are useful to investigate the sites of coordination of Mg2+ to ATP. At pH 3.0, comparable frequency shifts were observed for the vibrations localized at individual PO2- groups together with intensity changes of main chain vibrations attributable to conformational isomerization in some of the ATP molecules. These infrared data can be interpreted as due to coexistence of .alpha.,.beta.-, .beta.,.gamma.-, and .alpha.,.gamma.-bidentates. At pH 7.5, an .alpha.-PO2- vibration shifted by the same frequency as that at pH 3.0, whereas .beta.-PO2- vibrations showed twice as large shifts as those at pH 3.0. A similarly strong interaction of Mg2+ with .gamma.-PO32- was also suggested by the frequency shift data. MgATP at pH 7.5 is, thus, supposed to be a mixture of .beta.,.gamma.-bidentate and .alpha.,.beta.,.gamma.-tridentate complexes. Implications of the present findings for enzymatic reactions involving MgATP are discussed.