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首页> 外文期刊>Biochemistry >Competition between Co(NH3)63+ and Inner Sphere Mg2+ Ions in the HDV Ribozyme
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Competition between Co(NH3)63+ and Inner Sphere Mg2+ Ions in the HDV Ribozyme

机译：HDV核酶中Co（NH3）63+与内球Mg2 +离子之间的竞争

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Divalent cations play critical structural and functional roles in many RNAs. While the hepatitisndelta virus (HDV) ribozyme can undergo self-cleavage in the presence ofmolar concentrations ofmonovalentncations, divalent cations such as Mg2nare required for efficient catalysis under physiological conditions.nMoreover, the cleavage reaction can be inhibited with Co(NH3)6n3n, an analogue of Mg(H2O)6n2n. Here, thenbinding ofMg2nand Co(NH3)6n3nto theHDV ribozyme is studied byRamanmicroscopic analysis of crystals.nRaman difference spectra acquired at different metal ion conditions reveal changes in the ribozyme. WhennMg2nalone is introduced to the ribozyme, inner sphere coordination ofMg(H2O)xn2n(x e 5) to nonbridgingnPO2n- oxygen and changes in base stretches and phosphodiester group conformation are observed. Innaddition, binding of Mg2ninduces deprotonation of a cytosine assigned to the general acid C75, consistentnwith solution studies.When Co(NH3)6n3nalone is introduced, deprotonation of C75 is again observed, as arendistinctive changes in base vibrational ringmodes and phosphodiester backbone conformation. In contrast tonMg2nbinding, Co(NH3)6n3nbinding does not perturb PO2n- group vibrations, consistent with its ability tonmake only outer sphere contacts. Surprisingly, competitive binding studies reveal that Co(NH3)6n3nionsndisplace some inner sphere-coordinatedmagnesiumspecies, including ions coordinated to PO2n- groups or thenN7 of a guanine, likely G1 at the active site. These observations contrast with the tenet that Co(NH3)6n3nionsndisplace only outer spheremagnesiumions.Overall, our data support two classes of inner sphereMg2n-PO2n-nbinding sites: sites that Co(NH3)6n3ncan displace and others it cannot.
机译：二价阳离子在许多RNA中起着至关重要的结构和功能作用。尽管肝炎三角洲病毒（HDV）核酶可以在摩尔浓度的单价结合存在下进行自我裂解，但在生理条件下有效催化仍需要二价阳离子（例如Mg2），此外，类似物Co（NH3）6n3n可以抑制裂解反应。的Mg（H2O）6n2n。在这里，然后通过晶体的拉曼显微镜分析研究了Mg2n和Co（NH3）6n3n与HDV核酶的结合。在不同金属离子条件下获得的nRaman差谱揭示了核酶的变化。当nMg2nalone被引入到核酶中时，Mg（H2O）xn2n（x e 5）与非桥联nPO2n-氧的内球配位和碱基延伸和磷酸二酯基构象的变化被观察到。与溶液研究一致，Mg2n的结合会导致胞嘧啶去质子化，这与溶液研究一致。当引入Co（NH3）6n3nalone时，由于基本振动环模式和磷酸二酯主链构象的明显变化，再次观察到C75的质子化。相比之下，tonMg2n绑定，Co（NH3）6n3n绑定不会干扰PO2n组的振动，这与其仅使外层球接触的能力一致。出人意料的是，竞争性结合研究表明，Co（NH3）6n3nionsn取代了一些内球配位的镁物种，包括与PO2n-基团或鸟嘌呤N7配位的离子，可能在活性位点为G1。这些观察结果与Co（NH3）6n3nionsn只能置换外层镁离子的宗旨形成鲜明对比。总体而言，我们的数据支持两类内球Mg2n-PO2n-n结合位点：Co（NH3）6n3n可以置换的位点和其他不能置换的位点。

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  • 来源
    《Biochemistry》 |2009年第50期|p.11961-11970|共10页
  • 作者

    Bo Gong Jui-Hui Chen Philip C. Bevilacqua Barbara L. Golden and Paul R. Carey;

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    ‡Department of Biochemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106,§Department ofBiochemistry, Purdue University, 175 South University Street, West Lafayette, Indiana 47907, and ) Department of Chemistry,The Pennsylvania State University, 104 Chemistry Building, University Park, Pennsylvania 16802;

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