Structural highlights
Publication Abstract from PubMedCorn, a 28-nucleotide RNA, increases yellow fluorescence of its cognate ligand 3,5-difluoro-4-hydroxybenzylidene-imidazolinone-2-oxime (DFHO) by >400-fold. Corn was selected in vitro to overcome limitations of other fluorogenic RNAs, particularly rapid photobleaching. We now report the Corn-DFHO co-crystal structure, discovering that the functional species is a quasisymmetric homodimer. Unusually, the dimer interface, in which six unpaired adenosines break overall two-fold symmetry, lacks any intermolecular base pairs. The homodimer encapsulates one DFHO at its interprotomer interface, sandwiching it with a G-quadruplex from each protomer. Corn and the green-fluorescent Spinach RNA are structurally unrelated. Their convergent use of G-quadruplexes underscores the usefulness of this motif for RNA-induced small-molecule fluorescence. The asymmetric dimer interface of Corn could provide a basis for the development of mutants that only fluoresce as heterodimers. Such variants would be analogous to Split GFP, and may be useful for analyzing RNA co-expression or association, or for designing self-assembling RNA nanostructures. A homodimer interface without base pairs in an RNA mimic of red fluorescent protein.,Warner KD, Sjekloca L, Song W, Filonov GS, Jaffrey SR, Ferre-D'Amare AR Nat Chem Biol. 2017 Sep 25. doi: 10.1038/nchembio.2475. PMID:28945234[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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