Walter A E, Wu M, Turner D H
Department of Chemistry, University of Rochester, New York 14627-0216, USA.
Biochemistry. 1994 Sep 20;33(37):11349-54. doi: 10.1021/bi00203a033.
UV melting and imino proton NMR studies show that the stabilities and structures of tandem GA mismatches in RNA are dependent upon the closing base pairs around these mismatches. Internal loops of sequence 5'XGAY3'3'YAGXS' and 5'XAGY3'3'YGAX5' in the middle of octanucleotides have a range of stabilities over 5 kcal/mol when XY is a Watson-Crick or GU pair. The order of stabilities for these internal loops is 5'-GGAC-3' > UGAG, CGAG > AGAU > UGAA > GGAU. The motifs GGAC, UGAG, and CGAG are stabilizing, while the other GA motifs are destabilizing. The GAGC motif is more stable than CAGG and CGAG, but less stable than GGAC. Chemical shifts for imino protons suggest that the G imino proton of each GA mismatch in 5'-GGAC-3', 5'-GAGC-3', and 5'-CAGG-3' [SantaLucia, J., Jr., Kierzek, R., & Turner, D. H. (1990) Biochemistry 29, 8813-8819] is involved in a hydrogen bond to the base A, whereas in other 5'-XGAY-3' sequences, it is not involved in a hydrogen bond to the base A.
紫外熔解和亚氨基质子核磁共振研究表明，RNA中串联GA错配的稳定性和结构取决于这些错配周围的封闭碱基对。当XY为沃森-克里克碱基对或GU碱基对时，八聚核苷酸中间序列5'XGAY3'3'YAGXS'和5'XAGY3'3'YGAX5'的内环具有超过5千卡/摩尔的一系列稳定性。这些内环的稳定性顺序为5'-GGAC-3' > UGAG、CGAG > AGAU > UGAA > GGAU。基序GGAC、UGAG和CGAG具有稳定作用，而其他GA基序则具有 destabilizing 作用（此处原文“destabilizing”未明确对应中文词汇，可保留英文）。GAGC基序比CAGG和CGAG更稳定，但比GGAC不稳定。亚氨基质子化学位移表明，5'-GGAC-3'、5'-GAGC-3'和5'-CAGG-3'中每个GA错配的G亚氨基质子[圣卢西亚，J.，Jr.，基尔泽克，R.，&特纳，D. H.（1990）《生物化学》29，8813 - 8819]与碱基A形成氢键，而在其他5'-XGAY-3'序列中，它不与碱基A形成氢键。
