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首页> 外文期刊>Biochemistry >NMR STUDIES OF THE EFFECTS OF THE 5'-PHOSPHATE GROUP ON CONFORMATIONAL PROPERTIES OF 5-METHYLAMINOMETHYLURIDINE FOUND IN THE FIRST POSITION OF THE ANTICODON OF ESCHERICHIA COLI TRNA(4)(ARG)
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NMR STUDIES OF THE EFFECTS OF THE 5'-PHOSPHATE GROUP ON CONFORMATIONAL PROPERTIES OF 5-METHYLAMINOMETHYLURIDINE FOUND IN THE FIRST POSITION OF THE ANTICODON OF ESCHERICHIA COLI TRNA(4)(ARG)

机译：核磁共振研究大肠杆菌（Escherichia Coli）TRNA（4）（ARG）anticodon的第一个位置上发现的5'-磷酸酯基对5-甲基-次甲基尿嘧啶构象性质的影响

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摘要

5-Methylaminomethyluridine (mnm(5)U) exists in the first position of the anticodon (position 34) of Escherichia coli tRNA(4)(Arg) for codons AGA/AGG. In the present study, the temperature dependence of the ribose-puckering equilibrium of pmnm(5)U was analyzed by proton NMR spectroscopy. Thus, the enthalpy difference (Delta H) between the C2'-endo and C3'-endo forms was obtained as 0.65 kcal . mol(-1). By comparison of the Delta H values of pU and pmnm(5)U, the 5-substitution was found to increase the relative stability of the C3'-endo form over the C2'-endo form significantly (by 0.56 kcal mol-l). Furthermore, this conformational ''rigidity'' was concluded to depend on the 5'-phosphate group, because nucleoside U exhibits only a negligible change in the ribose-puckering equilibrium upon the 5-methylaminomethyl substitution. Further NMR analyses and molecular dynamics calculations revealed that interactions between the 5-methylaminomethyl and 5'-phosphate groups of pmnm(5)U restrict the conformation about the glycosidic bond to a low anti form, enhancing steric repulsion between the 2-carbonyl and 2'-hydroxyl groups in the C2'-endo form. This intrinsic conformational rigidity of the mnm(5)U residue in position 34 may contribute to the correct codon recognition.
机译：5-甲基氨基甲基尿苷（mnm（5）U）存在于大肠杆菌tRNA（4）（Arg）的AGA / AGG密码子反密码子的第一个位置（第34位）。在本研究中，通过质子NMR光谱分析了pmnm（5）U核糖折叠平衡的温度依赖性。因此，获得的C2′-内基和C3′-内基之间的焓差（ΔH）为0.65kcal。 mol（-1）。通过比较pU和pmnm（5）U的Delta H值，发现5-取代显着提高了C3'-内切形式相对于C2'-内切形式的相对稳定性（提高了0.56 kcal mol-1）。 。此外，该构象的“刚性”被认为取决于5'-磷酸基团，因为核苷U在5-甲基氨基甲基取代后在核糖起皱平衡中仅表现出微不足道的变化。进一步的NMR分析和分子动力学计算表明pmnm（5）U的5-甲基氨基甲基和5'-磷酸基团之间的相互作用将糖苷键的构象限制为低反形式，从而增强了2-羰基和2之间的空间排斥C2'-内基形式的'-羟基。在位置34的mnm（5）U残基的这种固有的构象刚度可能有助于正确的密码子识别。

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