Comparison of the hammerhead cleavage reactions stimulated by monovalent and divalent cations
Comparison of the hammerhead cleavage reactions stimulated by monovalent and divalent cations
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DOI：
10.1017/s1355838201002461
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发表时间：
2001-04-01
期刊：
影响因子：
4.5
通讯作者：
Herschlag, D
中科院分区：
文献类型：
--
作者：
O'Rear, JL;Wang, SL;Herschlag, D
尽管锤头反应在二价阳离子中进行得最有效，但在4 M LiCl中的裂解仅类似于比在IOmM MgCl 2的标准条件下慢10倍（Murray等人，Chem Biol，1998，5：587-595; Curtis & Bartel，RNA，2001，this issue，pp. 546-552）。为了确定高浓度一价阳离子的催化机理是否与二价阳离子的催化机理相似，我们比较了一系列修饰的锤头状核酶在两种离子条件下的活性。几乎所有的修饰在两种反应条件下都具有相似的有害作用，这表明锤头采用具有单价和二价阳离子的相同的一般催化结构，然而，先前与功能性二价金属离子的结合有关的三个配体的修饰对Li+中的裂解速率的影响显著小于对Mg 2+中的裂解速率的影响。这一结果表明，单价反应中不存在与该二价金属离子产生的相互作用类似的相互作用。虽然这种二价金属离子对总反应速率的贡献相对较小，但需要它的存在来实现完全的催化速率。这种离子的作用似乎是促进活性结构的形成，并且金属离子在锤头状催化中的任何直接化学作用都很小。
Although the hammerhead reaction proceeds most efficiently in divalent cations, cleavage in 4 M LiCl is only similar to 10-fold slower than under standard conditions of 10 mM MgCl2 (Murray et al,, Chem Biol, 1998, 5:587-595; Curtis & Bartel, RNA, 2001, this issue, pp. 546-552), To determine if the catalytic mechanism with high concentrations of monovalent cations is similar to that with divalent cations, we compared the activities of a series of modified hammerhead ribozymes in the two ionic conditions, Nearly all of the modifications have similar deleterious effects under both reaction conditions, suggesting that the hammerhead adopts the same general catalytic structure with both monovalent and divalent cations, However, modification of three ligands previously implicated in the binding of a functional divalent metal ion have substantially smaller effects on the cleavage rate in Li+ than in Mg2+. This result suggests that an interaction analogous to the interaction made by this divalent metal ion is absent in the monovalent reaction. Although the contribution of this divalent metal ion to the overall reaction rate is relatively modest, its presence is needed to achieve the full catalytic rate, The role of this ion appears to be in facilitating formation of the active structure, and any direct chemical role of metal ions in hammerhead catalysis is small.