Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309, USA.
RNA. 2010 Dec;16(12):2370-83. doi: 10.1261/rna.2385310. Epub 2010 Oct 12.
The invariant choice of L-amino acids and D-ribose RNA for biological translation requires explanation. Here we study this chiral choice using mixed, equimolar D-ribose RNAs having 15, 18, 21, 27, 35, and 45 contiguous randomized nucleotides. These are used for simultaneous affinity selection of the smallest bound and eluted RNAs using equal amounts of L- and D-His immobilized on an achiral glass support, with racemic histidine elution. The experiment as a whole therefore determines whether RNA containing D-ribose binds L-histidine or D-histidine more easily (that is, by using a site that is more abundant/requires fewer nucleotides). The most prevalent/smallest RNA sites are reproducibly and repeatedly selected and there is a four- to sixfold greater abundance of L-histidine sites. RNA's chiral D-ribose therefore yields a more frequent fit to L-histidine. Accordingly, a D-ribose RNA site for L-His is smaller by the equivalent of just over one conserved nucleotide. The most prevalent L-His site also performs better than the most frequent D-His site-but rarer D-ribose RNAs can bind D-His with excellent affinity and discrimination. The prevalent L-His site is one we have selected before under very different conditions. Thus, selection is again reproducible, as is the recurrence of cognate coding triplets in these most probable L-His sites. If our selected RNA population were equilibrated with racemic His, we calculate that L-His would participate in seven of eight His:RNA complexes, or more. Thus, if D-ribose RNA were first chosen biologically, translational L-His usage could have followed.
生物翻译中 L-氨基酸和 D-核糖 RNA 的不变选择需要解释。在这里，我们使用具有 15、18、21、27、35 和 45 个连续随机核苷酸的混合等摩尔 D-核糖 RNA 研究这种手性选择。这些用于同时使用等量的 L-和 D-His 固定在非手性玻璃载体上进行亲和力选择最小结合和洗脱的 RNA，使用外消旋组氨酸洗脱。因此，整个实验决定了含有 D-核糖的 RNA 是更容易结合 L-组氨酸还是 D-组氨酸（即使用更丰富/需要更少核苷酸的位点）。最普遍/最小的 RNA 位点可重复且反复选择，并且 L-组氨酸位点的丰度增加了四到六倍。因此，RNA 的手性 D-核糖与 L-组氨酸的匹配更频繁。因此，L-His 的 D-核糖 RNA 位点比 D-His 的小，相当于刚好超过一个保守核苷酸。最普遍的 L-His 位点也比最常见的 D-His 位点表现更好-但更罕见的 D-核糖 RNA 可以与 D-His 结合，具有极好的亲和力和区分力。最普遍的 L-His 位点是我们以前在非常不同的条件下选择的位点。因此，选择是可重复的，这些最可能的 L-His 位点中也会重复出现互补编码三联体。如果我们选择的 RNA 群体与外消旋 His 达到平衡，我们计算 L-His 将参与其中七个 His:RNA 复合物中的八个，或者更多。因此，如果 D-核糖 RNA 首先在生物学上被选择，那么翻译中的 L-His 使用就可以随之而来。
