Cation trafficking propels RNA hydrolysis
Cation trafficking propels RNA hydrolysis
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DOI：
10.1038/s41594-018-0099-4
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发表时间：
2018-08-01
影响因子：
16.8
通讯作者：
Yang, Wei
中科院分区：
文献类型：
--
作者：
Samara, Nadine L.;Yang, Wei
一般认为，RNA酶H超家族成员的催化作用仅需要两个由活性位点羧酸根配位的Mg 2+离子。然而，通过研究耐盐芽孢杆菌RNA酶H1在晶体中的催化过程，我们发现两个典型的Mg 2+离子和一个额外的K+未能对齐亲核水进行RNA切割。基板对齐和产品的形成需要第二个K+和第三个Mg 2+，它取代了第一个K+和离开后立即裂解。在DNA合成中也观察到了第三种瞬时Mg 2+，但在这种情况下，它与离去基团配位，而不是与RNase H1水解反应中的亲核试剂配位。这些瞬时阳离子与酶没有接触。在单个活性位点催化连续切割和链转移反应的其他DNA和RNA酶可能类似地需要由底物协调的阳离子运输。
Catalysis by members of the RNase H superfamily of enzymes is generally believed to require only two Mg2+ ions that are coordinated by active-site carboxylates. By examining the catalytic process of Bacillus halodurans RNase H1 in crystallo, however, we found that the two canonical Mg2+ ions and an additional K+ failed to align the nucleophilic water for RNA cleavage. Substrate alignment and product formation required a second K+ and a third Mg2+, which replaced the first K+ and departed immediately after cleavage. A third transient Mg2+ has also been observed for DNA synthesis, but in that case it coordinates the leaving group instead of the nucleophile as in the case of the RNase H1 hydrolysis reaction. These transient cations have no contact with the enzymes. Other DNA and RNA enzymes that catalyze consecutive cleavage and strand-transfer reactions in a single active site may similarly require cation trafficking coordinated by the substrate.