Functional group substitutions as probes of hydrogen bonding between GA mismatches in RNA internal loops
作者:John SantaLucia、Ryszard Kierzek、Douglas H. Turner
DOI:10.1021/ja00011a039
日期:1991.5
The contribution of hydrogen bonding to the stability of GA mismatches in RNA is investigated by making functional group substitutions. Such substitutions are made possible by the chemical synthesis of RNA; chemical incorporation of purine riboside and 2-aminopurine riboside into oligoribonucleotides is reported. In particular, replacing the 6-amino groups of internal loop adenosines with hydrogen atoms in (rGCGAGCG)2, (rGGCGAGCC)2, (rGCAGGCG)2, and (rCGCAGGCG)2 destabilizes the duplexes by 2.8, 3.0, 3.2, and 2.7 kcal/mol, respectively. The results suggest hydrogen bonding within each GA mismatch contributes at least -1.4 kcal/mol to duplex stability. Results on control sequences in which the internal loop residues are changed to inosine, 2-aminopurine riboside, or purine riboside are consistent with this interpretation. The results provide insight into the source of the unusual stability of RNA duplexes with internal loops containing GA mismatches (Santa Lucia, J., Jr.; Kierzek, R.; Turner, D. H. Biochemistry 1990, 29, 8813-8819). In contrast to GA mismatches in internal loops, hydrogen bonding between GA mismatches at the ends of oligonucleotide helices does not make a large contribution to helix stability. The implications of these results for predicting RNA structure are discussed.