glmS Riboswitch binding to the glucosamine-6-phosphate α-anomer shifts the pKa toward neutrality.
glmS Riboswitch binding to the glucosamine-6-phosphate α-anomer shifts the pKa toward neutrality.
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DOI：
10.1021/bi200471c
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发表时间：
2011-08-23
期刊：
影响因子：
2.9
通讯作者：
Strobel SA
中科院分区：
文献类型：
--
作者：
Davis JH;Dunican BF;Strobel SA
glmS核糖开关通过自切割活性调节基因表达。该反应在代谢物辅因子葡糖胺-6-磷酸（GlcN 6P）的协助下催化，其氨基在反应期间被提议用作一般酸。该反应是pH依赖性的，其pKa低于溶液中GlcN 6P的胺的所观察到的pKa。与其他吡喃糖一样，GlcN 6P在C1位的α和β端基异构体之间发生自发和快速的相互转化。在这里，我们通过NMR证明炭疽芽孢杆菌glmS核糖开关选择性地结合GlcN 6P的α-端基异构体，最大结合亲和力为0.36 mM，并且结合是pH依赖性的。我们还报告了α和β之间的异头比是pH依赖性的，两种胺的pKa相差0.5个pH单位，α是两者中较高的（pKa = 8.3）。结合的pH依赖性揭示了6.7的pKa，表明glmS RNA在基态将GlcN 6P胺的pKa降低了1.6个单位。我们重新评估了先前获得的动力学数据，发现反应pKa为6.9，在结合数据的误差范围内。数据支持反应pKa对应于GlcN 6P胺的pKa的模型。这一观察结果对于考虑RNA的微环境如何降低用于催化的官能团的pKa具有更广泛的相关性，尽管其具有阴离子特性。
The glmS riboswitch regulates gene expression through a self-cleavage activity. The reaction is catalyzed with the assistance of the metabolite cofactor glucosamine-6-phosphate (GlcN6P), whose amino group is proposed to serve as the general acid during the reaction. This reaction is pH-dependent with a pKa that is lower than the observed pKa for the amine of GlcN6P in solution. GlcN6P, like other pyranose sugars, undergoes spontaneous and rapid interconversion between the α and β anomers at the C1 position. Here we demonstrate by NMR that the Bacillus anthracis glmS riboswitch selectively binds the α-anomer of GlcN6P with a maximum binding affinity of 0.36 mM, and that binding is pH-dependent. We also report that the anomeric ratio between α and β is pH-dependent and the pKas of the two amines differ by 0.5 pH units, α being the higher of the two (pKa = 8.3). The pH dependence of binding reveals a pKa of 6.7, suggesting that the glmS RNA reduces the pKa of the GlcN6P amine by 1.6 units in the ground state. We reevaluated previously obtained kinetic data and found the reaction pKa is 6.9, within error of the binding data. The data support a model where the reaction pKa corresponds to that of the GlcN6P amine. This observation has broader relevance for considering how the microenvironment of an RNA, despite its anionic character, can reduce the pKas of functional groups for use in catalysis.
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影响因子：
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作者：
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通讯作者：
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影响因子：
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影响因子：
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作者：
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