The GlcN6P cofactor plays multiple catalytic roles in the glmS ribozyme.
The GlcN6P cofactor plays multiple catalytic roles in the glmS ribozyme.
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DOI：
10.1038/nchembio.2300
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发表时间：
2017-04
影响因子：
14.8
通讯作者：
Bevilacqua PC
中科院分区：
文献类型：
--
作者：
Bingaman JL;Zhang S;Stevens DR;Yennawar NH;Hammes-Schiffer S;Bevilacqua PC
尽管化学多样性有限，但RNA酶具有非常多样的生物学作用。蛋白质酶通过招募辅因子来增强其反应性。天然存在的glmS核酶利用氨基葡萄糖 - 6 - 磷酸（GlcN6P）有机辅因子进行磷酸二酯键的切割。先前的结构和生化研究表明GlcN6P是广义酸。在此，我们通过实验和计算描述了GlcN6P的新催化作用。全核酶中较大的立体特异性正常硫效应以及金属离子无法挽救反应表明，核碱基和辅因子发挥直接的化学作用，并使活性位点排列以进行自我切割。无辅因子核酶中较大的立体特异性反向硫效应表明，GlcN6P辅因子破坏了亲核试剂的抑制性相互作用。无辅因子核酶中金属离子的强烈挽救作用表明该辅因子还提供静电稳定作用。因此，核酶有机辅因子发挥多种催化作用，使RNA能够弥补其有限的功能多样性。
RNA enzymes have remarkably diverse biological roles despite having limited chemical diversity. Protein enzymes enhance their reactivity through recruitment of cofactors. The naturally occurring glmS ribozyme uses the glucosamine-6-phosphate (GlcN6P) organic cofactor for phosphodiester bond cleavage. Prior structural and biochemical studies implicated GlcN6P as the general acid. Here we describe new catalytic roles for GlcN6P through experiments and calculations. Large stereospecific normal thio effects and lack of metal ion rescue in the holoribozyme show that nucleobases and the cofactor play direct chemical roles and align the active site for self-cleavage. Large stereospecific inverse thio effects in the aporibozyme suggest that the GlcN6P cofactor disrupts an inhibitory interaction of the nucleophile. Strong metal ion rescue in the aporibozyme reveals this cofactor also provides electrostatic stabilization. Ribozyme organic cofactors thus perform myriad catalytic roles, allowing RNA to compensate for its limited functional diversity.