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首页> 外文期刊>Journal of Biomolecular Structure and Dynamics >Conformational Preferences of Anticodon 3 - Adjacent Hypermodified Nucleic Acid Base cis-or trans-Zeatin and its 2- methylthio Derivative, cis-or trans- ms(2)Zeatin.
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Conformational Preferences of Anticodon 3 - Adjacent Hypermodified Nucleic Acid Base cis-or trans-Zeatin and its 2- methylthio Derivative, cis-or trans- ms(2)Zeatin.

机译：反密码子3的构象偏好-相邻的超修饰核酸碱基顺式或反式玉米素及其2-甲硫基衍生物，顺式或反式ms（2）玉米素。

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摘要

Conformational preferences of the hypermodified nucleic acid bases N6-(Delta(2) -cis-hydroxyisopentenyl)adenine, cis- io(6)Ade also known as cis-zeatin, and N(6)- (Delta(2) -trans-hydroxyisopentenyl)adenine, trans- io(6)ade or trans-zeatin, and 2-methylthio derivatives of these cis-ms(2)io(6)Ade or cis- ms(2)zeatin, and trans-ms(2)io6Ade or trans- ms(2)zeatin have been investigated theoretically by the quantum chemical Perturbative Configuration Interaction with Localized Orbitals (PCILO) method. Automated geometry optimization using quantum chemical MNDO, AM1 and PM3 methods has also been made to compare the salient features. The predicted most stable conformation of cis-io(6)Ade, trans-io(6)Ade, cis- ms(2)io(6)Ade and trans- ms(2)io(6)Ade are such that in each of these molecules the isopentenyl substituent spreads away (has "dista" conformation) from the five membered ring imidazole moiety of the adenine. The atoms N(6), C(10) and C(11) remain coplanar with the adenine ring in the predicted preferred conformation for each of these molecules. In cis-io(6)Ade as well as cis- ms(2)io(6)Ade the hydroxyl oxygen may participate in intramolecular hydrogen bonding with the H-C(10)-H group. In trans-io(6)Ade the hydroxyl group is oriented towards the H-C(2) instead. This orientation is retained in trans- ms(2)io(6)Ade, possible O-H S hydrogen bonding may be a stabilizing factor. In all these four modified adenines C(11)-H is favourably placed to participate in intramolecular hydrogen bonding with N(1). In cis-ms(2)io(6)Ade as well as trans-ms(2)io(6)Ade the 2-methylthio group preferentially orients on the same side as C(2)-N(3) bond, due to this nonobstrusive placing, orientation of the hydroxyisopentenyl substituent remains unaffected by 2-methylthiolation. Thus the N(1) site remains shielded irrespective of the 2-methylthiolation status in these various cis-and trans-zeatin analogs alike. Firmly held orientation of hydroxyisopentenyl substituent in zeatin isomers and derivatives, in contrast to adaptable orientation of isopentenyl substituent in i(6)Ade and ms(2)i(6)Ade, may account for the increased efficiency of suppressor tRNA and reduced codon context sensitivity accompanied with the occurrence of ms(2)-zeatin (ms(2)io(6)Ade) modification.
机译：高度修饰的核酸碱基N6-（Delta（2）-顺式-羟基异戊烯基）腺嘌呤，顺式-io（6）Ade也称为顺式玉米素和N（6）-（Delta（2）-反式-羟基异戊烯基）腺嘌呤，反式-io（6）ade或反式玉米素，以及这些顺式-ms（2）io（6）Ade或顺式-ms（2）玉米素和反式ms（2）的2-甲硫基衍生物理论上已经通过量子化学微扰构型与局部轨道相互作用（PCILO）方法研究了io6Ade或trans-ms（2）玉米素。还使用量子化学MNDO，AM1和PM3方法进行了自动几何优化，以比较其显着特征。 cis-io（6）Ade，trans-io（6）Ade，cis-ms（2）io（6）Ade和trans-ms（2）io（6）Ade的预测最稳定构象在这些分子中，异戊烯基取代基从腺嘌呤的五元环咪唑部分扩散开（具有“ dista”构象）。对于这些分子中的每一个，原子N（6），C（10）和C（11）与腺嘌呤环保持共面且处于预测的优选构象。在顺式-io（6）Ade和顺式-ms（2）io（6）Ade中，羟基氧可能与H-C（10）-H基团参与分子内氢键合。在反式-io（6）Ade中，羟基改为朝向H-C（2）。该方向保留在trans-ms（2）io（6）Ade中，可能的O-HS氢键可能是稳定因素。在所有这四个修饰的腺嘌呤中，C（11）-H位置优越，可参与与N（1）的分子内氢键键合。在顺式ms（2）io（6）Ade和反式ms（2）io（6）Ade中，2-甲硫基优先与C（2）-N（3）键位于同一侧对于这种非干扰性的放置，羟基异戊烯基取代基的取向保持不受2-甲基硫醇化的影响。因此，在这些各种顺式和反式玉米素类似物中，无论2-甲基硫醇化状态如何，N（1）位点均保持屏蔽状态。与i（6）Ade和ms（2）i（6）Ade中的异戊烯基取代基的适应性取向相反，玉米色素异构体和衍生物中羟基异戊烯基取代基的牢固保持取向可解释抑制子tRNA效率提高和密码子减少的原因敏感性与ms（2）-玉米蛋白（ms（2）io（6）Ade）修饰的出现有关。

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