The displacement of copper by iron at the specific binding sites of ovotransferrin.
The displacement of copper by iron at the specific binding sites of ovotransferrin.
复制标题
在卵转铁蛋白的特异性结合位点上，铜被铁取代。
DOI：
10.1016/0304-4165(89)90005-6
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Bates,GW
中科院分区：
文献类型：
--
作者：
Chen,XX;Fas,N;Bates,GW
我们已经研究了铁可以取代铜在特定的金属结合位点的卵转铁蛋白的动力学和机制。在NaHCO 3和环境O2存在下，将Fe 2+加入到Cu 2 +-卵转铁蛋白-CO 32 −中。该反应已遵循标准和停流分光光度法，EPR光谱和分析显色反应的Fe 2+。该反应最好描述为三相反应。吸光度的初始跳跃发生在前2秒。在接下来的一分钟内，吸光度进一步增加，光谱最大值从440 nm移动到446 nm。第三个阶段是复杂的。大部分的分光光度变化，吸光度下降，最大值移动到453 nm，持续约10分钟。然而，在接下来的几个小时内，光谱和EPR发生了微小的变化。Fe ~（2+）的显色分析表明，氧化Fe ~（2+）需要1 min。EPR光谱显示在前20 s内形成了Fe 3 +-卵转铁蛋白复合物;然而，这缺乏特定Fe 3 +-卵转铁蛋白-CO 32 −的特征性双峰。同时存在特异性Cu 2 +-卵转铁蛋白-CO 32 −和Fe 3 +-卵转铁蛋白-CO 32 −s信号表明蛋白质特异性结合两种金属离子的时期，这可能是由于两种金属结合位点的差异反应性。Cu（NO3）2与Fe 3 +-ovotransferrin-CO 32 −形成特异性Fe 3+和非特异性Cu 2+的复合物。该络合物的EPR谱与我们的置换反应的最终产物几乎相同。Cu ~（2+）-卵转铁蛋白-CO_3 ~（2-）与Fe（NH_4）_2（SO_4）_2、Fe（NO_3）_3和Fe ~（3+）-硝基三乙酸的反应具有明显的相似性。提出了一个涉及非特异性Fe 2+结合和氧化、随后在特定位点用Fe 3+置换Cu 2+以及非特异性Cu 2+结合的反应序列。
We have examined the kinetics and mechanism by which iron can displace copper at the specific metal-binding sites of ovotransferrin. Fe2+was added to Cu2+-ovotransferrin-CO32−in the presence of NaHCO3and ambient O2. The reaction has been followed by standard and stopped-flow spectrophotometry, EPR spectroscopy and analysis of chromogen-reactive Fe2+. The reaction is best described as triphasic. An initial jump in absorbance takes place in the first 2 s. In the next minute there is a further increase in absorbance and shift in the spectral maximum from 440 to 446 nm. The third phase is complex. The bulk of the spectrophotometric change, a decrease in absorbance with a shift to a maximum of 453 nm, lasts approx. 3 min. Minor spectral and EPR changes, however, take place over the next several hours. Chromogenic analysis of Fe2+indicates that approx. 1 min is reqired to oxidize the Fe2+. EPR spectra reveal the formation of an Fe3+-ovotransferrin complex within the first 20 s; however, this lacks the characteristic doublet of specific Fe3+-ovotransferrin-CO32−. The simultaneous presence of specific Cu2+-ovotransferrin-CO32−and Fe3+-ovotransferrin-CO32−s signals suggests a period in which the protein specifically binds both metal ions perhaps resulting from a differential reactivity of the two metal-binding sites. The addition of Cu(NO3)2to Fe3+-ovotransferrin-CO32−resulted in a complex with specific Fe3+and non-specific Cu2+. The EPR spectrum of this complex and the final product of our displacement reaction were virtually identical. Distinct parallels in reaction of Cu2+-ovotransferrin-CO32−with Fe(NH4)2(SO4)2, Fe(NO3)3and Fe3+-nitrolotriacetic acid were observed. A reaction sequence involving the binding and oxidation of non-specific Fe2+followed by Cu2+displacement by Fe3+at the specific sites and binding of non-specific Cu2+is suggested.