• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Chemistry: A European journal >De novo metallonucleases based on helix-loop-helix motifs
【24h】

De novo metallonucleases based on helix-loop-helix motifs

机译：从头开始的金属核酸基于螺旋-环-螺旋基序

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

Three new 42-mer peptides (PRI-III) designed to fold into a hairpin helix-loop-helix motif have been prepared. In the peptide sequence two (PRII-III) or four (PRI) copies of an unnatural amino acid bearing a triazacyclononane metal-ion binding site (ATANP) have been inserted in appropriate positions to allow the ligand subunits to face each other either within the same helix or between the two helices of the hairpin motif. Circular dichroism (CD) studies in solution have shown that the apopeptides adopt a well-defined helix-loop-helix tertiary structure that dimerizes in solution at concentrations above 200 pm to form a four-helix bundle. However, the helical content is strongly dependent on pH and metal-ion binding. Both protonation of the amines of the triazacyclononane units present in the ATANP lateral arm and complexation with Zn-II ions cause a significant decrease of the helical content of the sequences. The Zn-II complexes of the three peptides catalyze the transesterification of the RNA model substrate 2-hydroxypropyl-p-nitrophenyl phosphate (HPNP) with different efficiency. The best catalyst appears to be PR I-4Zn(II), that is, the peptide incorporating four ATANP units. Michaelis-Menten saturation kinetics allowed us to estimate that substrate fully bound to the catalyst reacts 380 times faster than in its absence. The kinetic evidence suggests cooperativity between (at least two) metal ions: one activating the nucleophilic species (directly or indirectly) and the other facilitating nucleophilic attack by coordination of the phosphate.
机译：制备了三种新的可折叠成发夹螺旋-环-螺旋基序的42-mer肽（PRI-III）。在肽序列中，带有三氮杂双环壬烷金属离子结合位点（ATANP）的非天然氨基酸的两个（PRII-III）或四个（PRI）副本已插入合适的位置，以使配体亚基彼此面对面相同的螺旋或发夹基序的两个螺旋之间。溶液中的圆二色性（CD）研究表明，凋亡肽采用定义明确的螺旋-环-螺旋三级结构，该结构在溶液中以高于200 pm的浓度二聚形成四螺旋束。但是，螺旋含量强烈地依赖于pH和金属离子结合。 ATANP侧臂中存在的三氮杂环壬烷单元的胺的质子化以及与Zn-II离子的络合都会导致序列的螺旋含量显着降低。这三种肽的Zn-II复合物以不同的效率催化RNA模型底物2-羟丙基-对硝基苯基磷酸酯（HPNP）的酯交换反应。最好的催化剂似乎是PR I-4Zn（II），即掺入四个ATANP单元的肽。 Michaelis-Menten饱和动力学使我们能够估计，完全结合到催化剂上的底物的反应比不存在时的反应快380倍。动力学证据表明（至少两种）金属离子之间具有协同作用：一种（直接或间接地）激活亲核物质，另一种通过磷酸根的配位促进亲核攻击。

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