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Structural complementation of the catalytic domain of pseudomonas exotoxin A

机译:假单胞菌外毒素A催化域的结构互补

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摘要

The catalytic moiety of Pseudomonas exotoxin A (domain III or PE3) inhibits protein synthesis by ADP-ribosylation of eukaryotic elongation factor 2. PE3 is widely used as a cytocidal payload in receptor-targeted protein toxin conjugates. We have designed and characterized catalytically inactive fragments of PE3 that are capable of structural complementation. We dissected PE3 at an extended loop and fused each fragment to one subunit of a heterospecific coiled coil. In vitro ADP-ribosylation and protein translation assays demonstrate that the resulting fusions - supplied exogenously as genetic elements or purified protein fragments - had no significant catalytic activity or effect on protein synthesis individually but, in combination, catalyzed the ADP-ribosylation of eukaryotic elongation factor 2 and inhibited protein synthesis. Although complementing PE3 fragments are catalytically less efficient than intact PE3 in cell-free systems, co-expression in live cells transfected with transgenes encoding the toxin fusions inhibits protein synthesis and causes cell death comparably as intact PE3. Complementation of split PE3 offers a direct extension of the immunotoxin approach to generate bispecific agents that may be useful to target complex phenotypes.
机译:假单胞菌外毒素A(结构域III或PE3)的催化部分通过真核生物延伸因子2的ADP-核糖基化抑制蛋白质合成。PE3广泛用作受体靶向的蛋白质毒素缀合物中的杀细胞有效载荷。我们已经设计并表征了PE3的催化无活性片段,该片段具有结构互补性。我们在一个延长的循环中解剖了PE3,并将每个片段融合到一个异种卷曲螺旋的一个亚基上。体外ADP核糖基化和蛋白质翻译测定表明,作为遗传元件或纯化的蛋白质片段外源提供的所得融合物对单独的蛋白质合成没有明显的催化活性或影响,但结合起来催化了真核生物延伸因子的ADP核糖基化2,抑制蛋白质合成。尽管互补的PE3片段在无细胞系统中的催化效率比完整的PE3低,但与编码毒素融合的转基因转染的活细胞中的共表达与完整的PE3相比抑制蛋白质合成并导致细胞死亡。分离的PE3的补充提供了免疫毒素方法的直接扩展,以生成可用于靶向复杂表型的双特异性试剂。

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