Structural highlights
Publication Abstract from PubMedStructural studies of modified nucleobases in RNA duplexes are critical for developing a full understanding of the stability and specificity of RNA base pairing. 2-Thio-uridine (s2U) is a modified nucleobase found in certain tRNAs. Thermodynamic studies have evaluated the effects of s2U on base pairing in RNA, where it has been shown to stabilize U:A pairs and destabilize U:G wobble pairs. Surprisingly, no high-resolution crystal structures of s2U-containing RNA duplexes have yet been reported. We present here two high-resolution crystal structures of heptamer RNA duplexes (5'-uagcs2Ucc-3' paired with 3'-aucgAgg-5' and with 3'-aucgUgg-5') containing s2U:A and s2U:U pairs, respectively. For comparison, we also present the structures of their native counterparts solved under identical conditions. We found that replacing O2 with S2 stabilizes the U:A base pair without any detectable structural perturbation. In contrast, an s2U:U base pair is strongly stabilized in one specific U:U pairing conformation out of four observed for the native U:U base pair. This s2U:U stabilization appears to be due at least in part to an unexpected sulfur-mediated hydrogen bond. This work provides additional insights into the effects of 2-thio-uridine on RNA base pairing. Crystal Structure Studies of RNA Duplexes Containing sU:A and sU:U Base Pairs.,Sheng J, Larsen A, Heuberger BD, Blain JC, Szostak JW J Am Chem Soc. 2014 Sep 16. PMID:25188906[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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