• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Molecular Biology >Time evolution of the quaternary structure of Escherichia coli aspartate transcarbamoylase upon reaction with the natural substrates and a slow, tight-binding inhibitor.
【24h】

Time evolution of the quaternary structure of Escherichia coli aspartate transcarbamoylase upon reaction with the natural substrates and a slow, tight-binding inhibitor.

机译：与天然底物和缓慢，紧密结合的抑制剂反应后，大肠杆菌天冬氨酸转氨甲酰酶季结构的时间演化。

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Here, we present a study of the conformational changes of the quaternary structure of Escherichia coli aspartate transcarbamoylase, as monitored by time-resolved small-angle X-ray scattering, upon combining with substrates, substrate analogs, and nucleotide effectors at temperatures between 5 and 22 degrees C, obviating the need for ethylene glycol. Time-resolved small-angle X-ray scattering time courses tracking the T-->R structural change after mixing with substrates or substrate analogs appeared to be a single phase under some conditions and biphasic under other conditions, which we ascribe to multiple ligation states producing a time course composed of multiple rates. Increasing the concentration of substrates up to a certain point increased the T-->R transition rate, with no further increase in rate beyond that point. Most strikingly, after addition of N-phosphonacetyl-l-aspartate to the enzyme, the transition rate was more than 1 order of magnitude slower than with the natural substrates. These results on the homotropic mechanism are consistent with a concerted transition between structural and functional states of either low affinity, low activity or high affinity, high activity for aspartate. Addition of ATP along with the substrates increased the rate of the transition from the T to the R state and also decreased the duration of the R-state steady-state phase. Addition of CTP or the combination of CTP/UTP to the substrates significantly decreased the rate of the T-->R transition and caused a shift in the enzyme population towards the T state even at saturating substrate concentrations. These results on the heterotropic mechanism suggest a destabilization of the T state by ATP and a destabilization of the R state by CTP and CTP/UTP, consistent with the T and R state crystallographic structures of aspartate transcarbamoylase in the presence of the heterotropic effectors.
机译：在这里，我们介绍了在时间介于5到20之间的条件下，结合时间，底物，底物类似物和核苷酸效应子，通过时间分辨小角度X射线散射监测的大肠杆菌天冬氨酸转氨甲酰酶季结构的构象变化研究。 22摄氏度，不需要乙二醇。与底物或底物类似物混合后，追踪T-> R结构变化的时间分辨小角X射线散射时间过程在某些条件下似乎是单相，而在其他条件下则是双相的，这归因于多种连接状态产生由多个比率组成的时程。将底物浓度增加到某个点会增加T-> R跃迁速率，超过该点则不会进一步增加速率。最为显着的是，在向酶中添加N-膦酰基乙酰基-1-天门冬氨酸后，其转化速率比天然底物要慢1个数量级。这些同质机制的结果与低亲和力，低活性或高亲和力，高活性的天冬氨酸的结构状态和功能状态之间的一致转变相一致。 ATP和底物的添加增加了从T到R状态的跃迁速率，也减少了R状态稳态相的持续时间。在底物上添加CTP或CTP / UTP的组合会显着降低T-> R跃迁的速率，甚至在饱和底物浓度下也导致酶群体向T状态转移。这些关于异质性机理的结果表明，ATP会破坏T状态，而CTP和CTP / UTP会破坏R状态，这与存在异质性效应子的天冬氨酸转氨甲酰酶的T和R状态晶体结构一致。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号