Читать книгу Chemistry and Biology of Non-canonical Nucleic Acids - Naoki Sugimoto - Страница 35

A-minor interactions are the most widely used in tertiary interaction of RNAs [24a]. These are characterized by insertion of minor groove edges of adenine nucleobases into minor groove of neighboring helices, preferentially where G·C base pairs are formed. Inserted adenine nucleobase forms hydrogen bonds with one or both of the 2′-hydroxyl group of the ribose in the base pair. There are various hydrogen bonding patterns in A-minor interactions (Figure 2.12). Formation of hydrogen bonds between bulged adenine and minor groove of the neighboring helix contributes to the stabilization of loop–helix and helix–helix interactions [25]. Although some of the A-minor interactions, which cause tight packing of the adenine nucleobase into the minor groove, could largely contribute to the thermodynamic stability of RNA tertiary structure [26], energetic contribution of each A-minor interaction is considered to be weaker than other tertiary interaction motifs with rigid structure characteristics. It is likely that the A-minor interaction plays roles assisting in the shaping of the tertiary structure of RNAs rather than stabilizing the structure.