Mn(2+)-sensing mechanisms of yybP-ykoY orphan riboswitches.
Mn(2+)-sensing mechanisms of yybP-ykoY orphan riboswitches.
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DOI：
10.1016/j.molcel.2015.02.016
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发表时间：
2015-03-19
期刊：
影响因子：
16
通讯作者：
Ke A
中科院分区：
文献类型：
--
作者：
Price IR;Gaballa A;Ding F;Helmann JD;Ke A
在细菌中，核糖开关的顺式基因调控是普遍存在的。yybP-ykoY核糖开关家族是相当广泛的，但其配体和功能仍然未知。在这里，我们将乳酸乳球菌yybP-ykoY核糖开关表征为Mn 2+依赖性转录开启核糖开关，对Mn 2+具有约30-40 μM的亲和力。我们进一步测定了它在2.7 nm处的晶体结构，以阐明金属传感机制。核糖开关类似于发夹，具有通过四向连接和三级对接接口拴系的两个同轴堆叠的螺旋。Mn 2+敏感区，战略上位于高度保守的对接界面，有两个金属结合位点。尽管一个位点耐受Mg 2+和Mn 2+两者的结合，但另一个位点强烈偏好Mn 2+，这是由于与恒定腺苷的N7的直接接触。诱变后获得无Mn ~（2+）的E. coli yybP-ykoY结构进一步揭示了Mn 2+结合与Mn 2+敏感区和适体结构域的稳定性相耦合。
Gene regulation in cis by riboswitches is prevalent in bacteria. The yybP-ykoY riboswitch family is quite widespread, yet its ligand and function remained unknown. Here we characterize the Lactococcus lactis yybP-ykoY riboswitch as a Mn2+-dependent transcription-ON riboswitch, with a ~30–40 μM affinity for Mn2+. We further determined its crystal structure at 2.7 Å to elucidate the metal sensing mechanism. The riboswitch resembles a hairpin, with two coaxially stacked helices tethered by a four-way junction and a tertiary docking interface. The Mn2+-sensing region, strategically located at the highly conserved docking interface, has two metal binding sites. Whereas the one site tolerates binding of both Mg2+ and Mn2+, the other site strongly prefers Mn2+ due to a direct contact from the N7 of an invariable adenosine. Mutagenesis and a Mn2+-free E. coli yybP-ykoY structure further reveal that Mn2+ binding is coupled with stabilization of the Mn2+-sensing region and the aptamer domain.