title: Structural basis for activity of highly efficient RNA mimics of green fluorescent protein.
abstract: GFP and its derivatives revolutionized the study of proteins. Spinach is a recently reported in vitro-evolved RNA mimic of GFP, which as genetically encoded fusions makes possible live-cell, real-time imaging of biological RNAs without resorting to large RNA-binding protein-GFP fusions. To elucidate the molecular basis of Spinach fluorescence, we solved the cocrystal structure of Spinach bound to its cognate exogenous chromophore, showing that Spinach activates the small molecule by immobilizing it between a base triple, a G-quadruplex and an unpaired G. Mutational and NMR analyses indicate that the G-quadruplex is essential for Spinach fluorescence, is also present in other fluorogenic RNAs and may represent a general strategy for RNAs to induce fluorescence of chromophores. The structure guided the design of a miniaturized 'Baby Spinach', and it provides a foundation for structure-driven design and tuning of fluorescent RNAs.
authors.affiliation: Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, Bethesda, Maryland, USA.
authors.forename: Katherine Deigan
authors.initials: KD
authors.lastname: Warner
authors.affiliation: Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, Bethesda, Maryland, USA.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Chen
authors.affiliation: Department of Pharmacology, Weill-Cornell Medical College, Cornell University, New York, New York, USA.
authors.forename: Wenjiao
authors.initials: W
authors.lastname: Song
authors.affiliation: Department of Pharmacology, Weill-Cornell Medical College, Cornell University, New York, New York, USA.
authors.forename: Rita L
authors.initials: RL
authors.lastname: Strack
authors.affiliation: Medical Research Council (MRC) Laboratory of Molecular Biology, Cambridge, UK.
authors.forename: Andrea
authors.initials: A
authors.lastname: Thorn
authors.affiliation: Department of Pharmacology, Weill-Cornell Medical College, Cornell University, New York, New York, USA.
authors.forename: Samie R
authors.initials: SR
authors.lastname: Jaffrey
authors.affiliation: Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, Bethesda, Maryland, USA.
authors.forename: Adrian R
authors.initials: AR
authors.lastname: Ferré-D'Amaré
mesh_terms: D001665:Binding Sites; D056831:Coordination Complexes / Q000737:chemistry; D018360:Crystallography, X-Ray; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D054856:G-Quadruplexes; D049452:Green Fluorescent Proteins / Q000737:chemistry*; D055029:Inverted Repeat Sequences; D008958:Models, Molecular; D018716:Molecular Mimicry; D011188:Potassium / Q000737:chemistry; D012313:RNA / Q000737:chemistry*; D053838:Scattering, Small Angle
chemical_list: D056831:Coordination Complexes; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins; D012313:RNA; D011188:Potassium