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Acta Crystallogr F Struct Biol Commun. 2019 Aug 1;75(Pt 8):547-551. doi: 10.1107/S2053230X19010136. Epub 2019 Aug 2.

Co-crystal structure of the iMango-III fluorescent RNA aptamer using an X-ray free-electron laser.

Author information

1
Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, Bethesda, Maryland, USA.
2
Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA.
3
Center for Free Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg, Germany.

Abstract

Turn-on aptamers are in vitro-selected RNAs that bind to conditionally fluorescent small molecules and enhance their fluorescence. Upon binding TO1-biotin, the iMango-III aptamer achieves the largest fluorescence enhancement reported for turn-on aptamers (over 5000-fold). This aptamer was generated by structure-guided engineering and functional reselection of the parental aptamer Mango-III. Structures of both Mango-III and iMango-III have previously been determined by conventional cryocrystallography using synchrotron X-radiation. Using an X-ray free-electron laser (XFEL), the room-temperature iMango-III-TO1-biotin co-crystal structure has now been determined at 3.0 Å resolution. This structural model, which was refined against a data set of ∼1300 diffraction images (each from a single crystal), is largely consistent with the structures determined from single-crystal data sets collected at 100 K. This constitutes a technical benchmark on the way to XFEL pump-probe experiments on fluorescent RNA-small molecule complexes.

KEYWORDS:

RNA structure; X-ray free-electron lasers; XFELS; fluorescence; fluorescence turn-on aptamers; iMango-III; room temperature

PMID:
31397326
PMCID:
PMC6688663
[Available on 2020-08-01]
DOI:
10.1107/S2053230X19010136

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