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首页> 外文期刊>Biochemistry >Mechanism of suramin-induced deoligomerization of tumor necrosis factor alpha.
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Mechanism of suramin-induced deoligomerization of tumor necrosis factor alpha.

机译：苏拉明诱导肿瘤坏死因子α的低聚的机制。

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摘要

Deoligomerization of human tumor necrosis factor alpha (TNF), spiked with 125I-labeled form, was studied quantitatively using size-exclusion chromatography and off-line monitoring with a gamma-counter. A detailed investigation of the oligomeric state of TNF was carried out as a function of its own concentration (0.3-7500 nM referred to the subunit, M(r) 17,000) in the absence or in the presence of various amounts (10, 100, 1000 microM) of suramin, an inhibitor of TNF biological activity in vitro, which promotes TNF deoligomerization. The dependence of trimeric form content on total TNF concentration was modeled with a sequential dissociation process (trimer-->dimer-->monomer) assuming an identical dissociation constant for each step, Kd1 = 0.2 nM. This model was used as the simplest for data fitting although, generally, no chromatographic resolution of dimeric species could be obtained. Best fitting of all data could be achieved with a model including a conformational change of TNF trimer into a state more prone to deoligomerization (Kd2 = 400 nM), which was favored by suramin binding. A kinetic study of TNF dissociation by the same method produced values for the deoligomerization rate of trimer: on the average, koff approximately 4 x 10(-5) S-1 (t1/2 approximately 5 h) between 4 and 20 degrees C with little dependence on suramin concentration; at 37 degrees C, a sizable increase is observed in the presence of 1 mM suramin (koff = 2.3 x 10(-4) S-1, t1/2 = 0.8 h). Data of suramin inhibition on TNF receptor binding, as obtained after incubation times much shorter than the above half-life of trimer, indicate that suramin binding to TNF trimer is the early mechanism of receptor binding inhibition.
机译：使用尺寸排阻色谱和伽马计数器离线监测定量研究了掺有125 I标记形式的人类肿瘤坏死因子α（TNF）的脱寡聚作用。在不存在或存在各种不同量（10，100，100 1000 microM）苏拉明（suramin），一种体外TNF生物学活性抑制剂，可促进TNF解聚。假定每个步骤的解离常数相同，Kd1 = 0.2 nM，则采用顺序解离过程（三聚体->二聚体->单体）对三聚体形式含量对总TNF浓度的依赖性进行建模。尽管通常无法获得二聚体物种的色谱分离度，但该模型被用作最简单的数据拟合方法。所有数据的最佳拟合都可以通过一个模型来实现，该模型包括将TNF三聚体的构象变化变为更易于去低聚的状态（Kd2 = 400 nM），这受到苏拉明结合的支持。用相同方法对TNF进行解离的动力学研究得出三聚体解聚速率的值：平均而言，在4至20摄氏度之间，koff约为4 x 10（-5）S-1（t1 / 2约为5 h），对苏拉明浓度的依赖性很小;在37°C下，在存在1 mM苏拉明的情况下观察到相当大的增加（koff = 2.3 x 10（-4）S-1，t1 / 2 = 0.8 h）。温育时间比上述三聚体的半衰期短得多的苏拉明对TNF受体结合的抑制数据表明，苏拉明与TNF三聚体的结合是受体结合抑制的早期机理。

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