Watson-Crick basepairing

The other example is, of course, DNA. In retrospect, it seems clear that there was hardly any other comparably fundamental reactivity principle on the territory of natural products chemistry waiting to be discovered than that we know today as Watson-Crick basepairing. 

Figure 6.25 An evolved ATP-binding RNA molecule. (A) The Watson-Crick basepairing pattern, (B) the folding pattern, and (C) a surface representation of an RNA molecule selected to bind adenosine nucleotides. The bound ATP is shown in part B, and the binding site is revealed as a deep pocket in part C.

Figure 3.1 Hydrogen bond formation in G-tetrad, parallel triplexes consisting of T X a-T and C x g-C triads, A-motif, and i-motif (Watson-Crick basepairing is shown with dashed bonds, and Hoogsteen or reversed Hoogsteen base-pairing is shown with hashed bonds).

The 2D SS-NOESY spectra (mixing time 120 ms and 200 ms, respectively) allowed identification of the regular Watson-Crick basepairs due to their typical NH - H5/H2/inter and intrastrand HT NOE crosspeak patterns. The NH resonances in the upper stem, G17, G18, and UlO (one resonance cluster at 12.40 ppm), and the ones from the bottom stem, G4, G26, G2, and Gl, could be assigned unambiguously. Furthermore, the quality of the spectra also permitted assignments of most NH2 resonances in those stem regions. 

The observation that prokaryotic RFl and RF2 exhibit specificity for different RNA sequences suggests that direct contacts are made between the release factors and the mRNA. These protein-RNA interactions contrast with the codon-anticodon contacts defined by Watson-Crick basepairing rules, and hint at a mechanism in which the proteins mimic bound tRNA. 

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